Daytime (astronomy) - Daytime Variations With Latitude and Seasons

Daytime Variations With Latitude and Seasons

Given that the Earth's own axis of rotation is inclined by about 23.5 degrees from the perpendicular (as compared to its orbital plane), the length of the daytime period varies with seasons on the planet's surface, depending on the observer's latitude. Areas experiencing summer are tilted toward the sun. Their tilt toward the sun leads to over half of the day being in daylight and warmer temperatures due to the increased directness of the sun's rays. While increased daylight can have some effect on the increased temperature in the summer, most of the increase in temperature is due to the directness of the sun, not the increased daylight. The high (near 90 degrees) angles of the sun is what causes the tropics to be warm while low (barely above the horizon) angles at the poles is what causes them to be cold. Hours of daylight having little effect on temperature can be seen with the poles still being cold in their respective summers despite 24 hours of daylight, while the equator is warm with only 12 hours of daylight.

Although the length of the daytime period is always twelve hours at the Equator, in all seasons, at all other latitudes the length varies with the season. During the winter, the daytime period is shorter than twelve hours; during the summer, it is longer than 12 hours. When it is winter north of the Equator, it is summer south of the Equator, and vice versa.