What’s the difference between Astronomical Fall and Meteorological Fall?

Dear Mr. Skilling,
My friends and I are confused by astronomical fall and meteorological or calendar fall. Can you explain?
Helen E. Baker
Dear Helen,
With meteorological fall still in its infancy, it’s a good time to address this frequently asked question. Astronomical seasons are defined by the spring and fall equinoxes and the summer and winter solstices. However, the beginning and ending dates vary slightly from year to year. That’s why meteorologists prefer to use four three-month meteorological seasons. In the Northern Hemisphere, June, July, and August define meteorological summer, while meteorological winter is made up of December, January, and February. The remaining months define meteorological spring and fall. Since climate records are tabulated monthly, defining a season in terms of three complete months makes comparisons and rankings a relatively easy task.

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