Cheyenne NWS: Today Is The First Day Of Meteorological Fall
The National Weather Service defines meteorological seasons--as opposed to calendar seasons--as follows:
Meteorologists and climatologists break the 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.