Meteorologists and climatologists use a slightly different time scale for meteorological seasons than for astronomical winter, spring, summer, and fall.
Learn about the difference between meteorological and astronomical seasons in the graphic and interactive version below!
See our changing seasons resource collection to learn more.
(Image credit: NOAA Office of Education)
View this graphic for the Southern Hemisphere
In the Southern Hemisphere, the seasons are reversed, where summer occurs when the South Pole is oriented towards the sun, and winter happens when the South Pole faces away.
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Why are there two different types of seasons?
Meteorological observing and forecasting led to the creation of seasons that make it much easier to calculate seasonal statistics. These seasons, which are closely tied to our civil calendar, are broken down into groupings of three months based on the annual temperature cycle.
Astronomical seasons are based on the natural phenomena of the position of the Earth in relation to the sun. The Earth’s annual trip around the sun forms the basis for the astronomical calendar in which seasons are defined by two solstices and two equinoxes.
Meteorological seasons
- The length of the meteorological seasons is more consistent than the astronomical seasons, ranging from 90 days for winter of a non-leap year to 92 days for spring and summer.
- We generally think of winter as the coldest time of the year. It includes December, January, and February.
- Summer is typically the warmest time of the year and includes June, July, and August.
- Spring and fall are the transition seasons. Meteorological spring consists of March, April, and May, while meteorological fall is made up of September, October, and November.
Astronomical seasons
- The start of winter and summer is based on whether the North Pole is oriented toward or away from the sun due to Earth's natural tilt.
- At the winter solstice, the North Pole is tilted away from the sun, whereas at the summer solstice, the North Pole is tilted toward the sun.
- The start of spring and fall are determined by when the sun’s path is aligned with the Earth’s equator. They occur halfway between the solstices.
- The dates shown describe the astronomical seasons for the Northern Hemisphere in 2022; the exact dates vary slightly from year to year.
Interactive graphic
Drag the white slider bar back and forth over the images to compare what defines meteorological versus astronomical seasons. (Credit: NOAA Office of Education)