Most folks think summer starts on June 21, fall arrives on Sept. 22, and so on. You know — the first day of the season marked neatly on the calendar.
But if you’ve ever stepped outside in early June and felt like you were already sweating through August, you’ve probably realized: nature doesn’t always follow the calendar’s schedule. That’s where meteorological seasons come in.
Meteorologists divide the year into four seasons, too — but we do it differently. For us, the seasons begin and end at the start of the month, like so:
■ Meteorological Spring: March 1 to May 31
■ Meteorological Summer: June 1 to Aug. 31
■ Meteorological Fall: Sept. 1 to Nov. 30
■ Meteorological Winter: Dec. 1 to Feb. 28 (or 29 in leap years)
So, why the difference? It’s all about consistency and climate data. The calendar seasons — the solstices and equinoxes—are based on the Earth’s position in orbit around the sun .
The summer solstice in June marks the longest day of the year, while the winter solstice in December gives us the shortest. Those dates can shift by a day or so each year, depending on leap years and how the calendar aligns.
Meteorological seasons, on the other hand, are purely based on the temperature patterns we observe over time. Climatologists and weather forecasters need tidy, consistent three-month blocks to compare data, things like average temperatures, rainfall, snowfall, and severe weather events.
Having fixed start and end dates makes it easier to track and study seasonal trends from one year to the next. Think about it: if we want to compare how warm this summer is shaping up compared to last year, it’s a lot easier if we use the same June 1 to Aug. 31 window every time.
If we used the astronomical calendar, we’d be starting and ending on slightly different days each year, making the data messier. And honestly? Most of us feel the shift in seasons long before the official equinox rolls around.
Spring often feels like it’s well underway by mid-March. Summer heat is usually in full swing by early June. And by the time September arrives, the air starts to crisp up, whether the calendar says “fall” or not.
Meteorological seasons don’t just make sense for data reflects how we experience the changing weather. So, next time someone tells you summer hasn’t started yet because it’s only June 10, feel free to tell them that, according to meteorologists, it’s been summer for over a week.
You’re not sweating in confusion, it’s science.
From my window (which is open on a muggy June morning), Dr. Nick
