Fall? Summer? Or is it both?

This is taken directly from NCEI (National Centers for Environmental Information) which is part of NOAA (National Oceanic and Atmospheric Administration). Both are part of NOAA. I bet you didn’t know that employees in the Federal Government spoke in acronyms! I had to reorient myself to speaking English when I retired from the NWS.

Meteorologists and climatologists define seasons differently from “regular” or “astronomical” spring, summer, fall, and winter. So, why do meteorological and astronomical seasons begin and end at different times? In short, it’s because the astronomical seasons are based on the position of Earth in relation to the sun, whereas the meteorological seasons are based on the annual temperature cycle.

The natural rotation of Earth around the sun forms the basis for the astronomical calendar, in which we define seasons with two solstices and two equinoxes. Earth’s tilt and the sun’s alignment over the equator determine both.

The equinoxes mark the times when the sun passes directly above the equator. In the Northern Hemisphere, the summer solstice falls on or around June 21, the winter solstice on or around Dec. 22, the vernal or spring equinox on or around March 21, and the autumnal equinox on or around Sept. 22. Variations in season length and season start make it very difficult to consistently compare climatological statistics for a particular season from one year to the next. Thus, the meteorological seasons were born.

Meteorologists and climatologists break seasons down into groupings of three months based on the annual temperature cycle as well as our calendar. We generally think of winter as the coldest time of the year and summer as the warmest time of the year, with spring and fall being the transition seasons, and that is what the meteorological seasons are based on. Meteorological spring includes March, April, and May; meteorological summer includes June, July, and August; meteorological fall includes September, October, and November; and meteorological winter includes December, January, and February.

Meteorological observing and forecasting led to the creation of these seasons, and they are more closely tied to our monthly calendar than astronomical seasons are. By following the civil calendar and having less variation in season length and season start, it becomes much easier to calculate seasonal statistics from monthly statistics, both of which are very useful for agriculture, commerce, and a variety of other purposes.