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The Seasons of the Year

The seasons of the year, unlike the days of the week or the months of the year are largely determined by natural and not man-made factors. The variations in temperature and climate on the Earth during different times of the year is largely a result of the tilt of the Earth.

Diagram Depicting Four Seasons

What Causes the Seasons of the Year

The axis of the Earth is tilted approximately 22.5° in reference to the Sun and the Earth's orbit. The tilt of the Earth always points in the same direction no matter where it happens to be positioned in its orbit. Thus, as the planet circles the sun, the axis is tilted more toward or away from the sun. Because the Earth relies on the sun for heat, the area closest to the sun will naturally be warmer. This happens nominally because of closer proximity, but mainly because there are more daylight hours. On the areas more oblique to the Sun's rays, the warming effect will be less because more of the rays will bounce off the atmosphere. During the summer in North America, the northern hemisphere is tilted generally toward the sun. This same time will constitute winter in the southern hemisphere, in Australia, for example, because the South Pole is pointing generally away from the sun.

The Earth's orbit around the sun is not exactly centered on the sun. The Earth is actually a bit closer to the sun in the Northern Hemisphere's winter, allowing 7% more direct sunlight during that timeframe1.

The point at which the axis of the Earth is pointed most toward the Sun is called the summer solstice. This marks the beginning of summer. Summer's end and autumn's beginning occurs on the autumnal equinox. The equinox occurs when the sun appears to be directly over the equator and the poles are "equidistant" from the sun. Autumn lasts until the winter solstice, which occurs toward the end of December. And thus, the seasons progress, with winter ending at the vernal equinox. Spring then lasts until the summer solstice rolls around again.

The seasons are thought to be distinct phases of the year: spring, the time of new life or rebirth; summer, the time of warmth and verdant growth; autumn, the time for harvest and gathering; winter, the time for sleep, rest and death. Nevertheless, there are in actuality only two legs of the seasonal cycle, that of warming, and that of cooling. Winter and summer derive from the time of stasis that seems to come about between the movement of the two trends.

The seasons are, of course, cyclical. They are usually presented in the order of their progression, beginning with spring, because spring is the season of birth. We will follow that convention here. To read about each of the seasons in order, please click on the next page link at the bottom of each page. To go directly to a season use the navigation bar at the top of each page.

Next Page: Spring


  1. WeatherQuestions.com



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