Meteorologists define seasons a little differently than most. Instead of using the periods between solstices and equinoxes (or vice versa), we go by calendar month. For example:
- Meteorological Spring: March, April, May
- Meteorological Summer: June, July, August
- Meteorological Fall: September, October, November
- Meteorological Winter: December, January, February
The more-often used “astronomical” definition of the seasons is not quite as simple. For example, a traditionally defined Winter would begin on the Winter Solstice (which can fall on December 21st or 22nd) and end on the Vernal Equinox (which can fall on March 19th, 20th, or 21st)
Because these dates are not consistent, the length of seasons can vary from year to year. That makes it very difficult for us in the weather industry to compute and meaningfully compare seasonal data, which is important for agriculture, trade, and much more.
Using our month-based definition instead, the amount of days in any given season is always the same… unless it’s a leap year! But that’s only one season every four years. It’s still more consistent, so we’ll take it!