The astronomical seasons that people are most familiar with begin and end on the solstices and equinoxes (which normally occur around Mar 21, June 21, Sept 22, and Dec 22). But, since the dates of the solstices and equinoxes vary slightly from year to year (because the earth takes about 365 1/4 days to go around the sun), meteorologists use whole months to define the “meteorological” seasons. The three normally coldest months in the Northern Hemisphere are December, January, and February, and are called “meteorological winter”. The three normally warmest months are June, July, and August, and are called “meteorological summer”. “Meteorological spring” includes the months of March, April, and May, and “meteorological autumn” includes the months of September, October, and November.