Seasons on Earth

As the Earth revolves around the Sun, the planet tilts 23.5 degrees on its axis of rotation. The degree to which various points on the globe are pointing toward or away from the Sun determines the seasons. The Northern and Southern hemispheres experience opposite seasons throughout the year.

Latitude is a key factor affecting the climate in a particular location on Earth. Because the Earth is a globe, the Sun's rays hit more directly at the equator than near the poles. This means the Sun's energy is more concentrated near the equator and more spread out near the poles. Average temperatures become cooler moving from the equator to higher latitudes.

In the Northern hemisphere, the summer solstice occurs on June 21 when the Sun's rays are directly hitting the Tropic of Cancer, 23.5 degrees north of the equator. Six months later, the winter solstice occurs on December 21 when the most direct sunlight hits the Tropic of Capricorn in the Southern hemisphere.

March 20 and September 22 are the equinox dates when the Sun's rays are directly hitting the Earth's equator. Neither hemisphere is tilted toward or away from the Sun. All locations on Earth experience approximately equal hours of day and night on these days.

Throughout the year, the tropical regions near the Earth's equator receive fairly direct sunlight. These regions experience little variation in daylight hours and temperature. There is little or no change in seasons in the tropics.

Regions located in the temperate zone latitudes experience four distinct seasons during the Earth's yearly cycle. Summer temperatures are warm because the Earth is tilted toward the Sun and there are more daylight hours. Winter temperatures are cold because the Earth is tilted away from the Sun and there are fewer daylight hours.

The Sun's rays hit the Earth's polar regions at very slanted angles. These regions have year-round cold temperatures and do not experience four distinct seasons. Instead, these areas have six months of daylight when the Earth's pole is tilted toward the Sun, followed by six months of darkness when the pole is tilted away from the Sun.