View source for Equator

{{Short description|Imaginary line halfway between Earth's North and South poles}}
{{About|Earth's equator|its projection in the sky|Celestial equator|other uses}}{{For|the country|Ecuador}}{{Location map-line|lat=0|caption=The equator on a [[world map|map of Earth]]}}
{{Use dmy dates|date=May 2025 |cs1-dates=ll}}

[[File:The Equator in boreal winter.gif|thumb|150px|right|The equator during the boreal winter, spanning from December to March. The direction of the Sun is to the left.]]

[[File:Equator_and_Prime_Meridian.svg|thumb|upright=1.35|Countries and territories that are intersected by the equator (red) or the [[IERS Reference Meridian|Prime Meridian]] (blue), which intersect at "[[Null Island]]".]]

The '''equator''' is the [[circle of latitude]] that divides [[Earth]] into the [[Northern Hemisphere|Northern]] and [[Southern Hemisphere|Southern]] [[Hemispheres of Earth|hemispheres]]. It is an [[imaginary line]] located at 0 degrees [[latitude]], about {{cvt|40,075|km}} in circumference, halfway between the [[North Pole|North]] and [[South Pole|South]] poles.<ref name="National">{{cite web |url=https://www.nationalgeographic.org/encyclopedia/equator/|title=Equator|website=National Geographic - Education|date=6 September 2011|access-date= 9 March 2021}}</ref> The term can also be used for any other celestial body that is roughly spherical.

In [[three-dimensional space|spatial (3D)]] [[geometry]], as applied in [[astronomy]], the equator of a rotating [[spheroid]] (such as a [[planet]]) is the parallel (circle of latitude) at which latitude is defined to be 0°. It is an [[imaginary line]] on the spheroid, equidistant from its [[geographical pole|poles]], dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the [[plane (geometry)|plane]] [[perpendicular]] to its axis of [[rotation]] and midway between its [[geographical pole]]s.

On and near the equator (on Earth), noontime [[sunlight]] appears almost directly overhead (no more than about 23° from the [[zenith]]) every day, year-round. Consequently, the equator has a rather stable daytime temperature throughout the year. On the [[equinox]]es (approximately 20 March and 23 September) the [[subsolar point]] crosses Earth's equator at a shallow angle, sunlight shines perpendicular to Earth's axis of rotation, and all latitudes have nearly a 12-hour day and 12-hour night.<ref>{{cite web |url=https://www.timeanddate.com/astronomy/equinox-not-equal.html#:~:text=Perfect%20opportunity%20to%20see%20the%20Midnight%20Sun%21%20On,equinoxes%20is%20how%20sunrise%20and%20sunset%20are%20defined.|title=Equinox: Almost Equal Day and Night |first1=Aparna |last1=Kher |website=timeanddate.com |access-date=5 November 2021}}</ref>

==Etymology==
The name is derived from [[medieval Latin]] word {{lang|la|aequator}}, in the phrase {{lang|la|circulus aequator diei et noctis}}, meaning 'circle equalizing day and night', from the [[Latin]] word {{lang|la|aequare}} 'make equal'.<ref>{{Cite web|url=https://en.oxforddictionaries.com/definition/equator|archive-url=https://web.archive.org/web/20180523011400/https://en.oxforddictionaries.com/definition/equator|url-status=dead|archive-date=23 May 2018|title=Definition of equator|website=Oxford Dictionaries|access-date=5 May 2018}}</ref>

==Overview==
{{multiple image
| align = right
| image1 = Equator monument.jpg
| width1 = 150
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| image2 = Equator sign kenya.jpg
| width2 = 125
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| footer = ''Left'': A monument marking the equator near the city of [[Pontianak, Indonesia]]<br />''Right'': Road sign marking the equator near [[Nanyuki]], [[Kenya]]
}}

The [[latitude]] of the Earth's equator is, by definition, 0° (zero [[degree (angle)|degrees]]) of arc. The equator is one of the five notable [[circle of latitude|circles of latitude]] on Earth; the other four are the two [[polar circle]]s (the [[Arctic Circle]] and the [[Antarctic Circle]]) and the two [[tropics|tropical circles]] (the [[Tropic of Cancer]] and the [[Tropic of Capricorn]]). The equator is the only line of latitude which is also a [[great circle]]—meaning, one whose [[Plane (mathematics)|plane]] passes through the center of the globe. The plane of Earth's equator, when projected outwards to the [[celestial sphere]], defines the [[celestial equator]].

In the cycle of Earth's [[season]]s, the equatorial plane runs through the Sun twice a [[year]]: on the [[equinox]]es in [[March equinox|March]] and [[September equinox|September]]. To a person on Earth, the Sun [[subsolar point|appears to travel along]] the equator (or along the celestial equator) at these times. 

[[File:Equator Sao Tome.jpg|thumb|The equator marked as it crosses [[Ilhéu das Rolas]], in [[São Tomé and Príncipe]]]]
[[File:equator Line Monument, Macapá city, Brazil.jpg|thumb|The Marco Zero monument marking the equator in [[Macapá]], [[Brazil]]]]

Locations on the equator experience the shortest [[sunrise]]s and [[sunset]]s because the Sun's [[sun path|daily path]] is nearly perpendicular to the [[horizon]] for most of the year. The length of [[daylight]] (sunrise to sunset) is almost constant throughout the year; it is about 14 minutes longer than nighttime due to [[atmospheric refraction]] and the fact that sunrise begins (or sunset ends) as the upper limb, not the center, of the Sun's disk contacts the horizon.

Earth [[equatorial bulge|bulges slightly]] at the equator; its average diameter is {{cvt|12742|km|mi}}, but the diameter at the equator is about {{cvt|43|km|mi}} greater than at the poles.<ref name="National"></ref>

Sites near the equator, such as the [[Guiana Space Centre]] in [[Kourou]], French Guiana, are good locations for [[spaceport]]s as they have the fastest [[rotational speed]] of any latitude, {{cvt|460.|m}}/sec. The added [[Delta-v|velocity]] reduces the fuel needed to launch spacecraft eastward (in the direction of Earth's rotation) to orbit, while simultaneously avoiding costly maneuvers to flatten [[inclination]] during missions such as the [[Apollo Program|Apollo Moon landings]].<ref name="Moonport">{{cite web |author1=William Barnaby Faherty |author2=Charles D. Benson |title=Moonport: A History of Apollo Launch Facilities and Operations |url=http://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |id=NASA Special Publication-4204 |series=NASA History Series |access-date=8 May 2019 |archive-url=https://web.archive.org/web/20180915105350/https://www.hq.nasa.gov/office/pao/History/SP-4204/contents.html |archive-date=15 September 2018 |page=Chapter 1.2: A Saturn Launch Site |date=1978 |quote=Equatorial launch sites offered certain advantages over facilities within the continental United States. A launching due east from a site on the equator could take advantage of the earth's maximum rotational velocity ({{cvt|460.|m/s}}) to achieve orbital speed. The more frequent overhead passage of the orbiting vehicle above an equatorial base would facilitate tracking and communications. Most important, an equatorial launch site would avoid the costly dogleg technique, a prerequisite for placing rockets into equatorial orbit from sites such as Cape Canaveral, Florida (28 degrees north latitude). The necessary correction in the space vehicle's trajectory could be very expensive - engineers estimated that doglegging a Saturn vehicle into a low-altitude equatorial orbit from Cape Canaveral used enough extra propellant to reduce the payload by as much as 80%. In higher orbits, the penalty was less severe but still involved at least a 20% loss of payload. |url-status=dead }}</ref>

==Geodesy==
{{further|Earth ellipsoid|Reference ellipsoid}}

===Precise location===
The precise location of the equator is not truly fixed; the true equatorial plane is perpendicular to the [[Earth's rotation axis]], which [[polar motion|drifts]] about {{convert|9|m|0}} during a year.

Geological samples show that the equator significantly changed positions between 48 and 12 million years ago, as sediment deposited by ocean thermal currents at the equator shifted. The deposits by thermal currents are determined by the axis of Earth, which determines solar coverage of [[Earth#Surface|Earth's surface]]. Changes in Earth's axis can also be observed in the geographical layout of volcanic island chains, which are created by shifting hot spots under Earth's crust as the axis and crust move.<ref>{{Cite web |title=Millions of Years Ago, the Poles Moved — And It Could Have Triggered an Ice Age |url=https://www.discovermagazine.com/environment/millions-of-years-ago-the-poles-moved-and-it-could-have-triggered-an-ice-age |date=26 November 2018 |first1=Anna |last1=Funk |website=Discover Magazine |language=en |url-status=live |archive-url= https://web.archive.org/web/20230924192144/https://www.discovermagazine.com/environment/millions-of-years-ago-the-poles-moved-and-it-could-have-triggered-an-ice-age |archive-date= 24 September 2023 }}</ref> This is consistent with the [[Indian Plate|Indian tectonic plate]] colliding with the [[Eurasian Plate|Eurasian tectonic plate]], which is causing the [[Himalaya]]n uplift.

===Exact length===
{{Main|Earth's circumference}}

The International Association of Geodesy (IAG) and the International Astronomical Union (IAU) use an equatorial radius of {{cvt|6,378.1366|km}} (codified as the IAU 2009 value).<ref>{{cite journal |url= http://www.sai.msu.ru/neb/rw/CelMech110.pdf |bibcode-access=free |s2cid-access=free |title= The IAU 2009 system of astronomical constants: the report of the IAU working group on numerical standards for Fundamental Astronomy |journal= Celest Mech Dyn Astr |date= 2011|volume= 110 |pages= 293–304 |doi= 10.1007/s10569-011-9352-4 |first1= Brian |last1= Luzum |first2= Nicole |last2= Capitaine |first3= Agnès |last3= Fienga |first4= William |last4= Folkner |first5= Toshio |last5= Fukushima |first6= James |last6= Hilton |first7= Catherine |last7= Hohenkerk |first8= George |last8= Krasinsky |first9= Gérard |last9= Petit |first10= Elena |last10= Pitjeva |first11= Michael |last11= Soffel |first12= Patrick |last12= Wallace |issue= 4 |bibcode= 2011CeMDA.110..293L|s2cid= 122755461 |doi-access= free |url-status=live |archive-url=https://web.archive.org/web/20230801102509/https://www.sai.msu.ru/neb/rw/CelMech110.pdf |archive-date= 1 August 2023 }}</ref> This equatorial radius is also in the 2003 and 2010 IERS Conventions.<ref>{{cite web|url = http://iers-conventions.obspm.fr/2010/2010_official/chapter1/tn36_c1.pdf|title= General definitions and numerical standards|work = IERS Technical Note 36 |archive-url=https://web.archive.org/web/20181218054401/http://iers-conventions.obspm.fr/2010/2010_official/chapter1/tn36_c1.pdf|archive-date = 18 December 2018}}</ref> It is also the equatorial radius used for the IERS 2003 ellipsoid. If it were really circular, the length of the equator would then be exactly 2π times the radius, namely {{cvt|40,075.0142|km}}. The [[GRS 80]] (Geodetic Reference System 1980) as approved and adopted by the IUGG at its Canberra, Australia meeting of 1979 has an equatorial radius of {{cvt|6,378.137|km}}. The [[WGS 84]] (World Geodetic System 1984) which is a standard for use in cartography, geodesy, and satellite navigation including [[Global Positioning System|GPS]], also has an equatorial radius of {{cvt|6,378.137|km}}. For both GRS 80 and WGS 84, this results in a length for the equator of {{cvt|40,075.0167|km}}.

The [[geographical mile]] is defined as one [[arc-minute]] of the equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is {{convert|1855.3248|m}}, while by IAU-2000, it is {{convert|1855.3257|m}}. This is a difference of less than {{Convert|1|mm|spell=in}} over the total distance (approximately {{convert|1.86|km||disp=or}}).

Earth is commonly modeled as a [[sphere]] flattened 0.336% along its axis. This makes the equator 0.16% longer than a [[meridian (geography)|meridian]] (a great circle passing through the two poles). The IUGG standard meridian is, to the nearest millimetre, {{convert|40007.862917|km}}, one arc-minute of which is {{convert|1852.216|m}}, explaining the [[International System of Units|SI]] standardization of the [[nautical mile]] as {{convert|1852|m}}, more than {{convert|3|m}} less than the [[geographical mile]].

The [[sea level|sea-level]] surface of Earth (the [[geoid]]) is irregular, so the actual length of the equator is not so easy to determine. ''[[Aviation week and space technology|Aviation Week and Space Technology]]'' on 9 October 1961 reported that measurements using the [[Transit (satellite)|Transit]] IV-A satellite had shown the equatorial diameter from longitude 11° West to 169° East to be {{convert|1000|ft|m|order=flip}} greater than its diameter ninety degrees away.<ref>{{cite magazine |last=Booda |first=Larry |date=9 October 1961 |title=Transit IV-A Proves Equator Is Elliptical |url=https://archive.aviationweek.com/issue/19611009 |url-access=subscription |magazine=Aviation Week and Space Technology |location=Washington, DC, USA |publisher=McGraw-Hill |pages=32-33 |department=Space Technology}}</ref>

==Equatorial countries and territories==
{{kml}}

[[File:ECSundialGPS.jpg|thumb|upright|[[Global Positioning System|GPS]] reading taken on the equator close to the [[Quitsato Sundial]], in [[Cayambe, Ecuador|Cayambe]], [[Ecuador]]<ref name="Informe que determina la posición de la Línea Ecuatorial">{{cite web|author=Instituto Geográfico Militar de Ecuador|title=Memoria Técnica de la Determinación de la Latitud Cero|url=https://www.scribd.com/doc/97475201/Documento-Posicionamiento-Reloj-Solar|date=24 January 2005|language=es}}</ref>]]
[[File:The Middle Ground (3960089271).jpg|thumb|Sign on the equator in [[San Antonio de Pichincha]], Ecuador.]]
[[File:Crossing the Equator (46217438471).jpg|thumb|The [[N1 road (Gabon)|N1 road]] crossing the equator in [[Gabon]], north of [[Bifoun]].]]

The equator passes over approximately 8714 km of land (21.7%) and 31,361 km of sea (78.3%).<ref>{{cite web | url=https://www.worldatlas.com/articles/countries-on-the-equator.html | title=Countries on the Equator | date=20 March 2019 }}</ref> It passes through the land of eleven [[sovereign state]]s. [[Indonesia]] is the country straddling the greatest length of the equatorial line across both land and sea. Starting at the [[IERS Reference Meridian|Prime Meridian]] and heading eastwards, the equator passes through:

{| class="wikitable plainrowheaders"
! style="width:10em;"| Coordinates
! style="width:14em;"| Country or<br />water body
! scope="col" | Notes
|-
| style="background:#b0e0e6;" | {{Coord|0|N|0|E|type:landmark|name=Prime Meridian}}
! scope="row" style="background:#b0e0e6;" | [[Atlantic Ocean]]
| style="background:#b0e0e6;" | [[Gulf of Guinea]], "[[Null Island]]"
|-
| {{Coord|0|0|N|6|31|E|type:country|name=São Tomé and Príncipe}}
! scope="row" | {{STP}}
| Passing through [[Pestana Equador]] resort on the [[Ilhéu das Rolas]]
|-
| {{Coord|0|0|N|9|21|E|type:country|name=Gabon}}
! scope="row" | {{GAB}}
| Passing {{convert|8.9|km|abbr=on}} south of [[Ayem]], {{convert|10.6|km|abbr=on}} north of [[Mayene]], [[Booue]]
|-
| {{Coord|0|0|N|13|57|E|type:country|name=Republic of the Congo}}
! scope="row" | {{Flag|COG|name=Congo}}
| Passing through the town of [[Makoua]].
|-
| {{Coord|0|0|N|17|45|E|type:country|name=Democratic Republic of the Congo}}
! scope="row" | {{Flag|COD|name=DR Congo}}
| Passing {{convert|9|km|abbr=on}} south of central [[Butembo]]
|-
| {{Coord|0|0|N|29|44|E|type:country|name=Uganda}}
! scope="row" | {{UGA}}
| Passing {{convert|32|km|abbr=on}} south of central [[Kampala]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|32|13|E|type:waterbody|name=Lake Victoria}}
! scope="row" style="background:#b0e0e6;" | [[Lake Victoria]]
| style="background:#b0e0e6;" | Passing through some islands of {{UGA}} in [[Mukono District]] and [[Namayingo District]]
|-
| {{Coord|0|0|N|34|0|E|type:country|name=Kenya}}
! scope="row" | {{KEN}}
| Passing {{convert|6|km|abbr=on}} north of central [[Kisumu]]. Passes through the highest mountain in [[Kenya]] i.e [[Mount Kenya]]
|-
| {{Coord|0|0|N|41|0|E|type:country|name=Somalia}}
! scope="row" | {{SOM}}
| Passing south of [[Jamame]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|42|53|E|type:waterbody|name=Indian Ocean}}
! scope="row" style="background:#b0e0e6;" | [[Indian Ocean]]
| style="background:#b0e0e6;" | Passing between [[Huvadhu Atoll]] and [[Fuvahmulah]] of {{MDV}}
|-
| {{Coord|0|0|N|98|13|E|type:country|name=Indonesia}}
! scope="row" | {{IDN}}
| [[North Sumatra]] ([[Batu Islands]]), [[West Sumatra]] ([[West Pasaman Regency|West Pasaman]], [[Pasaman Regency|Pasaman]] and [[Lima Puluh Kota Regency]]), [[Riau]] ([[Kampar Regency|Kampar]], [[Pelalawan Regency|Pelalawan]] and [[Indragiri Hilir Regency]]), and [[Lingga Regency]] of [[Riau Islands]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|104|35|E|type:waterbody|name=South China Sea}}
! scope="row" style="background:#b0e0e6;" | [[South China Sea]]
| style="background:#b0e0e6;" |
|-
| {{Coord|0|0|N|109|10|E|type:country|name=Indonesia}}
! scope="row" | {{IDN}}
| [[Borneo|Bornean]] provinces of [[West Kalimantan]] (passing through province capital [[Pontianak, Indonesia|Pontianak]]), [[Central Kalimantan]], and [[East Kalimantan]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|117|31|E|type:waterbody|name=Makassar Strait}}
! scope="row" style="background:#b0e0e6;" | [[Makassar Strait]]
| style="background:#b0e0e6;" | 
|-
| {{Coord|0|0|N|119|40|E|type:country|name=Indonesia}}
! scope="row" | {{IDN}}
| [[Donggala Regency|Donggala]] & [[Parigi Moutong Regency]], [[Central Sulawesi|Central Sulawesi (Celebes)]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|120|6|E|type:waterbody|name=Gulf of Tomini}}
! scope="row" style="background:#b0e0e6;" | [[Gulf of Tomini]]
| style="background:#b0e0e6;" |
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|123|22|E|type:waterbody|name=Molucca Sea}}
! scope="row" style="background:#b0e0e6;" | [[Molucca Sea]]
| style="background:#b0e0e6;" |
|-
| {{Coord|0|0|N|127|25|E|type:country|name=Indonesia}} 
! scope="row" | {{IDN}}
|[[Kayoa]] and [[Halmahera]] islands, [[North Maluku]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|127|53|E|type:waterbody|name=Halmahera Sea}}
! scope="row" style="background:#b0e0e6;" | [[Halmahera Sea]]
| style="background:#b0e0e6;" |
|-
| {{Coord|0|0|N|129|21|E|type:country|name=Indonesia}}
! scope="row" | {{IDN}}
| [[Gebe]] and Kawe islands, [[North Maluku]], [[Southwest Papua]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|130|11|E|type:waterbody|name=Pacific Ocean}}
! scope="row" style="background:#b0e0e6;" | [[Pacific Ocean]]
| style="background:#b0e0e6;" | Passing between [[Aranuka]] and [[Nonouti]] atolls, {{KIR}} (at {{Coord|0|0|N|173|45|E}})<br>Also passing just south of [[Baker Island]], and just north of [[Jarvis Island]], {{UMI}}
|-
| {{Coord|0|0|N|91|35|W|type:country|name=Ecuador}}
! scope="row" | {{ECU}}
| [[Isabela Island (Ecuador)|Isabela Island]] in the [[Galápagos Islands]]
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|91|13|W|type:waterbody|name=Pacific Ocean}}
! scope="row" style="background:#b0e0e6;" | [[Pacific Ocean]]
| style="background:#b0e0e6;" | 
|-
| {{Coord|0|0|N|80|7|W|type:country|name=Ecuador}}
! scope="row" | {{ECU}}
| Passing {{convert|24|km|abbr=on}} north of central [[Quito]], near [[Ciudad Mitad del Mundo|Mitad del Mundo]], and precisely at the location of [[Catequilla]], a [[Pre-Columbian era|pre-Columbian]] ruin.
|-
| {{Coord|0|0|N|75|35|W|type:country|name=Colombia}}
! scope="row" | {{COL}}
| Passing {{convert|4.3|km|abbr=on}} north of the border with [[Peru]]
|-valign="top"
| {{Coord|0|0|N|70|3|W|type:country|name=Brazil}}
! scope="row" | {{BRA}}
| [[Amazonas (Brazilian state)|Amazonas]], [[Roraima]], [[Pará]], [[Amapá]] (passing slightly south of the city center of the state capital [[Macapá]], and precisely at the Marco Zero monument and the Avenue Equatorial)
|-
| style="background:#b0e0e6;" | {{Coord|0|0|N|49|21|W|type:waterbody|name=Atlantic Ocean}}
! scope="row" style="background:#b0e0e6;" | [[Atlantic Ocean]]
| style="background:#b0e0e6;" | At the [[Perigoso Canal]] on the mouth of the [[Amazon River]]
|-
|}

The equator also passes through the [[Territorial waters#Territorial sea|territorial seas]] of three countries: [[Maldives]] (south of [[Gaafu Dhaalu Atoll]]), [[Kiribati]] (south of [[Buariki (Aranuka)|Buariki Island]]), and the [[United States]] (south of [[Baker Island]]).

Despite its name, no part of [[Equatorial Guinea]] lies on the equator. However, its island of [[Annobón]] is {{convert|155|km|abbr=on}} south of the equator, and the rest of the country lies to the north. [[France]], [[Norway]] ([[Bouvet Island]]), and the [[United Kingdom]] are the other three [[Northern Hemisphere]]-based countries which have territories in the [[Southern Hemisphere]].

==Equatorial seasons and climate==
{{Main|Season|Effect of Sun angle on climate}}
{{See|Tropics}}

[[File:seasons.svg|frame|right|<br />Diagram of the seasons, showing the situation at the December solstice. Regardless of the time of day (i.e. [[Earth]]'s rotation on its axis), the [[North Pole]] will be dark, and the [[South Pole]] will be illuminated; see also [[polar night]] and [[polar day]]. In addition to the density of [[angle of incidence (optics)|incident]] light, the [[dissipation]] of light in [[atmosphere of Earth|atmosphere]] is greater when it falls at a shallow angle. Note that the equator is not under the [[subsolar point]] during this time of year.]] 

Seasons result from the tilt of Earth's axis away from a line perpendicular to the plane of its revolution around the Sun. Throughout the year, the Northern and Southern hemispheres are alternately turned either toward or away from the Sun, depending on Earth's position in its orbit. The hemisphere turned toward the Sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter (see [[solstice]]).

At the [[equinox]]es, Earth's axis is perpendicular to the Sun rather than tilted toward or away, meaning that day and night are both about 12 hours long across the whole of Earth.

Near the equator, this means the variation in the strength of solar radiation is different relative to the time of year than it is at higher latitudes: maximum solar radiation is received during the equinoxes, when a place at the equator is under the [[subsolar point]] at high noon, and the intermediate seasons of spring and autumn occur at higher latitudes; and the minimum occurs during ''both'' solstices, when either pole is tilted towards or away from the sun, resulting in either summer or winter in both hemispheres. This also results in a corresponding movement of the equator away from the subsolar point, which is then situated over or near the relevant [[Tropic of Cancer|tropic]] [[Tropic of Capricorn|circle]]. Nevertheless, temperatures are high year-round due to the Earth's [[axial tilt]] of 23.5° not being enough to create a low minimum midday [[Position of the Sun#Declination of the Sun as seen from Earth|declination]] to sufficiently weaken the Sun's rays even during the solstices. High year-round temperatures extend to about 25° north or south of the equator, although the moderate seasonal temperature difference is defined by the opposing solstices (as it is at higher latitudes) near the poleward limits of this range.   

Near the equator, there is little temperature change throughout the year, though there may be dramatic differences in rainfall and humidity. The terms summer, autumn, winter and spring do not generally apply. Lowlands around the equator generally have a [[tropical rainforest climate]], also known as an equatorial climate, though cold ocean currents cause some regions to have [[tropical monsoon climate]]s with a [[dry season]] in the middle of the year, and the [[Somali Current]] generated by the [[monsoon of South Asia|Asian monsoon]] due to continental heating via the high [[Tibetan Plateau]] causes [[Greater Somalia]] to have an arid climate despite its equatorial location.

Average annual temperatures in equatorial lowlands are around {{convert|31|°C|°F|abbr=on}} during the afternoon and {{convert|23|°C|°F|abbr=on}} around sunrise. Rainfall is very high away from cold ocean current upwelling zones, from {{convert|2500|to|3500|mm|abbr=on|round=5}} per year. There are about 200 rainy days per year and average annual sunshine hours are around 2,000. Despite high year-round sea level temperatures, some higher altitudes such as the [[Andes]] and [[Mount Kilimanjaro]] have glaciers. The highest point on the equator is at the elevation of {{convert|4690|m|0}}, at {{Coord|0|0|0|N|77|59|31|W|type:landmark_region:EC|name=highest point on the equator}}, found on the southern slopes of [[Cayambe (volcano)|Volcán Cayambe]] [summit {{convert|5790|m|0}}] in [[Ecuador]]. This is slightly above the [[snow line]] and is the only place on the equator where snow lies on the ground. At the equator, the snow line is around {{convert|1000|m|ft}} ''lower'' than on [[Mount Everest]] and as much as {{convert|2000|m|ft}} lower than the highest snow line in the world, near the [[Tropic of Capricorn]] on [[Llullaillaco]].

{{Weather box|width=75%
|location = [[Libreville]], [[Gabon]] in Africa
|metric first = yes
|single line = yes
|temperature colour = pastel
|Jan high C = 29.5
|Feb high C = 30.0
|Mar high C = 30.2
|Apr high C = 30.1
|May high C = 29.4
|Jun high C = 27.6
|Jul high C = 26.4
|Aug high C = 26.8
|Sep high C = 27.5
|Oct high C = 28.0
|Nov high C = 28.4
|Dec high C = 29.0
|year high C = 28.58
|Jan mean C = 26.8
|Feb mean C = 27.0
|Mar mean C = 27.1
|Apr mean C = 26.6
|May mean C = 26.7
|Jun mean C = 25.4
|Jul mean C = 24.3
|Aug mean C = 24.3
|Sep mean C = 25.4
|Oct mean C = 25.7
|Nov mean C = 25.9
|Dec mean C = 26.2
|year mean C = 25.95
|Jan low C = 24.1
|Feb low C = 24.0
|Mar low C = 23.9
|Apr low C = 23.1
|May low C = 24.0
|Jun low C = 23.2
|Jul low C = 22.1
|Aug low C = 21.8
|Sep low C = 23.2
|Oct low C = 23.4
|Nov low C = 23.4
|Dec low C = 23.4
|year low C = 23.30
|rain colour = green
|Jan rain mm = 250.3
|Feb rain mm = 243.1
|Mar rain mm = 363.2
|Apr rain mm = 339.0
|May rain mm = 247.3 
|Jun rain mm = 54.1
|Jul rain mm = 6.6
|Aug rain mm = 13.7
|Sep rain mm = 104.0
|Oct rain mm = 427.2
|Nov rain mm = 490.0
|Dec rain mm = 303.2
|Jan rain days = 17.9
|Feb rain days = 14.8
|Mar rain days = 19.5
|Apr rain days = 19.2
|May rain days = 16.0
|Jun rain days = 3.70
|Jul rain days = 1.70
|Aug rain days = 4.90
|Sep rain days = 14.5
|Oct rain days = 25.0
|Nov rain days = 22.6
|Dec rain days = 17.6
|unit rain days = 0.1 mm
|Jan sun = 176.7
|Feb sun = 182.7
|Mar sun = 176.7
|Apr sun = 177.0
|May sun = 158.1
|Jun sun = 132.0
|Jul sun = 117.8
|Aug sun = 89.90
|Sep sun = 96.00
|Oct sun = 111.6
|Nov sun = 135.0
|Dec sun = 167.4
|year sun = 1720.9
|source 1 = [[World Meteorological Organization]] ([[United Nations|UN]]),<ref>{{cite web
 |url=http://www.worldweather.org/128/c00255.htm
 |title=Weather Information for Libreville
 |website = World Weather Information Service
 |publisher = World Meteorological Organization}}</ref> [[Hong Kong Observatory]]<ref>{{cite web|url = http://www.weather.gov.hk/wxinfo/climat/world/eng/africa/nig_cam/libreville_e.htm |title = Climatological Normals of Libreville|website = Hong Kong Observatory |archive-url =https://web.archive.org/web/20191026001210/http://www.weather.gov.hk/wxinfo/climat/world/eng/africa/nig_cam/libreville_e.htm|archive-date = 26 October 2019}}</ref>
|date = March 2011
}}<br />

{{Weather box|width=75%
|location = [[Pontianak]], [[Indonesia]] in Asia
|metric first = yes
|single line = yes
|temperature colour = pastel
|Jan high C = 32.4
|Feb high C = 32.7
|Mar high C = 32.9
|Apr high C = 33.2
|May high C = 33.0
|Jun high C = 33.2
|Jul high C = 32.9
|Aug high C = 33.4
|Sep high C = 32.6
|Oct high C = 32.6
|Nov high C = 32.2
|Dec high C = 32.0
|year high C = 32.7
|Jan mean C = 27.6
|Feb mean C = 27.7
|Mar mean C = 28.0
|Apr mean C = 28.2
|May mean C = 28.2
|Jun mean C = 28.2
|Jul mean C = 27.7
|Aug mean C = 27.9
|Sep mean C = 27.6
|Oct mean C = 27.7
|Nov mean C = 27.4
|Dec mean C = 27.2
|year mean C = 27.7
|Jan low C = 22.7
|Feb low C = 22.6
|Mar low C = 23.0
|Apr low C = 23.2
|May low C = 23.4
|Jun low C = 23.1
|Jul low C = 22.5
|Aug low C = 22.3
|Sep low C = 22.6
|Oct low C = 22.8
|Nov low C = 22.6
|Dec low C = 22.4
|year low C = 22.7
|rain colour = green
|Jan rain mm = 260
|Feb rain mm = 215
|Mar rain mm = 254
|Apr rain mm = 292
|May rain mm = 256
|Jun rain mm = 212
|Jul rain mm = 201
|Aug rain mm = 180
|Sep rain mm = 295
|Oct rain mm = 329
|Nov rain mm = 400
|Dec rain mm = 302
|Jan rain days = 15
|Feb rain days = 13
|Mar rain days = 21
|Apr rain days = 22
|May rain days = 20
|Jun rain days = 18
|Jul rain days = 16
|Aug rain days = 25
|Sep rain days = 14
|Oct rain days = 27
|Nov rain days = 25
|Dec rain days = 22
|unit rain days = 0.1 mm
|source 1 = [[World Meteorological Organization]] ([[United Nations|UN]])<ref>{{cite web
 |url=http://www.worldweather.org/043/c00653.htm
 |title=Weather Information for Pontianak
 |website = World Weather Information Service
 |publisher = World Meteorological Organization}}</ref>
|date = March 2011
}}<br />

{{Weather box|width=75%
|location = [[Macapá]], [[Brazil]] in South America
|metric first = yes
|single line = yes
|temperature colour = pastel
|Jan high C = 29.7
|Feb high C = 29.2
|Mar high C = 29.3
|Apr high C = 29.5
|May high C = 30.0
|Jun high C = 30.3
|Jul high C = 30.6
|Aug high C = 31.5
|Sep high C = 32.1
|Oct high C = 32.6
|Nov high C = 32.3
|Dec high C = 31.4
|year high C = 30.71
|Jan mean C = 26.5
|Feb mean C = 26.2
|Mar mean C = 26.3
|Apr mean C = 26.4
|May mean C = 26.8
|Jun mean C = 26.8
|Jul mean C = 26.8
|Aug mean C = 27.4
|Sep mean C = 27.8
|Oct mean C = 28.1
|Nov mean C = 27.9
|Dec mean C = 27.4
|year mean C = 27.03
|Jan low C = 23.0
|Feb low C = 23.1
|Mar low C = 23.2
|Apr low C = 23.5
|May low C = 23.5
|Jun low C = 23.2
|Jul low C = 22.9
|Aug low C = 23.3
|Sep low C = 23.4
|Oct low C = 23.5
|Nov low C = 23.5
|Dec low C = 23.4
|year low C = 23.29
|rain colour = green
|Jan rain mm = 299.6
|Feb rain mm = 347.0
|Mar rain mm = 407.2
|Apr rain mm = 384.3
|May rain mm = 351.5
|Jun rain mm = 220.1
|Jul rain mm = 184.8
|Aug rain mm = 98.0
|Sep rain mm = 42.6
|Oct rain mm = 35.5
|Nov rain mm = 58.4
|Dec rain mm = 142.5
|Jan rain days = 23
|Feb rain days = 22
|Mar rain days = 24
|Apr rain days = 24
|May rain days = 25
|Jun rain days = 22
|Jul rain days = 19
|Aug rain days = 13
|Sep rain days = 6
|Oct rain days = 5
|Nov rain days = 6
|Dec rain days = 14
|unit rain days = 0.1 mm
|Jan sun = 148.8
|Feb sun = 113.1
|Mar sun = 108.5
|Apr sun = 114.0
|May sun = 151.9
|Jun sun = 189.0
|Jul sun = 226.3
|Aug sun = 272.8
|Sep sun = 273.0
|Oct sun = 282.1
|Nov sun = 252.0
|Dec sun = 204.6
|year sun = 2336.1
|source 1 = [[World Meteorological Organization]] ([[United Nations|UN]]),<ref>{{cite web
 |url=http://www.worldweather.org/136/c01071.htm
 |title=Weather Information for Macapa
 |website = World Weather Information Service 
 |publisher = World Meteorological Organization}}</ref> [[Hong Kong Observatory]]<ref>{{cite web|url = http://www.weather.gov.hk/wxinfo/climat/world/eng/s_america/brazil/macapa_e.htm |title = Climatological Normals of Macapa|website =Hong Kong Observatory |archive-url =https://web.archive.org/web/20191026000816/http://www.weather.gov.hk/wxinfo/climat/world/eng/s_america/brazil/macapa_e.htm |archive-date = 26 October 2019}}</ref>
|date = March 2011
}}

==Line-crossing ceremonies==
{{Main|Line-crossing ceremony}}

There is a widespread maritime tradition of holding ceremonies to mark a sailor's first crossing of the equator. In the past, these ceremonies have been notorious for their brutality, especially in naval practice. {{citation needed|date=April 2017}} Milder line-crossing ceremonies, typically featuring [[Neptune (mythology)|King Neptune]], are also held for passengers' entertainment on some civilian ocean liners and cruise ships.{{citation needed|date=January 2015}}

==See also==
{{portal|Geography}}
{{div col}}
* [[1st parallel north]]
* [[1st parallel south]]
* [[Bogota Declaration]]
* [[Coriolis force]]
* [[Intertropical Convergence Zone]]
* [[Planetary coordinate system#Ellipsoid of revolution (spheroid)|Planetary equator]]
* [[IERS Reference Meridian|Prime meridian]]
* [[Thermal equator]]
{{div col end}}

==References==
{{reflist}}

==Sources==
{{Commons category|Equator}}
{{refbegin}}
* {{cite journal |title=Geodetic Reference System 1980 |journal=Bulletin Géodésique |publisher=[[Springer-Verlag]] |location=[[Berlin]] |first=H |last=Moritz |pages=395–405 |volume=54 |issue=3 |date=September 1980 |doi=10.1007/BF02521480|bibcode = 1980BGeod..54..395M |s2cid=198209711 }} (IUGG/WGS-84 data)
* {{cite book |title=Computational Spherical Astronomy |publisher=Wiley |location=[[New York City|New York]] |first=Laurence G |last=Taff |year=1981 |isbn=0-471-06257-X |oclc=6532537}} (IAU data)
{{refend}}

{{Geographical coordinates|state=collapsed}}

{{Authority control}}

[[Category:Astronomical coordinate systems]]
[[Category:Circles of latitude]]
[[Category:Geodesy]]
[[Category:Tropics]]