'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
incident light, the
dissipation of light in the
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
equinoxes, 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 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
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 climates with a
dry season in the middle of the year, and the
Somali Current generated by the
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 during the afternoon and around sunrise. Rainfall is very high away from cold ocean current upwelling zones, from 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 , at , found on the southern slopes of
Volcán Cayambe [summit ] 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
lower than on
Mount Everest and as much as lower than the highest snow line in the world, near the
Tropic of Capricorn on
Llullaillaco.
Hong Kong Observatory }} }}
Hong Kong Observatory }} ==Line-crossing ceremonies==