Understanding the Start of Summer

Summer might not officially begin until June 20 with the summer solstice, but meteorologists and climatologists actually consider June 1 the beginning of summer.

This is because the astronomical seasons are based on the Earth’s position relative to the Sun, while “meteorological” or “climatological” seasons are divided into three-month periods based on the temperatures that would be expected during each season.

Astronomical vs. Meteorological Seasons

The start of summer depends on whether you’re referring to the astronomical or the meteorological start. (FOX Weather)

For example, summer is the hottest time of the year and winter is the coldest time of the year, with fall and spring being the transition seasons. So, instead of focusing on the Earth’s orientation to the Sun, these so-called meteorological seasons are solely classified by the annual temperature cycle across the world.

Meteorological Seasons

The hottest three months of the year in the Northern Hemisphere are June, July and August, so meteorological summer runs from June 1 to Aug. 31.

HEAT ALERTS ARE GETTING NEW NAMES THIS SUMMER FROM THE NATIONAL WEATHER SERVICE

Conversely, December, January and February are the Northern Hemisphere’s coldest three months, so meteorological winter runs from Dec. 1 to Feb. 28 (or Feb. 29).

The transition seasons are the three months between summer and winter, so meteorological fall is Sept. 1 to Nov. 30 and meteorological spring is March 1 to May 31.

Boardwalk to a beach. Getty Images

Why Meteorological Seasons Matter

Splitting the seasons into these nearly equal three-month periods makes seasonal recordkeeping much easier since the start and end dates of the seasons are always the same. Additionally, each meteorological season is always 90 to 92 days, depending on whether it’s a leap year or not.

The dates of the solstices and equinoxes can vary by a day or two each year, so an apples-to-apples comparison of seasonal temperatures or precipitation would become a nightmare for our friends at the National Weather Service if they didn’t use meteorological seasons.

Astronomical Summer

In 2025, astronomical summer officially begins on June 20, with the summer solstice at 10:42 p.m. EDT. That’s simply the precise moment in time when the Sun will be in direct alignment with the Tropic of Cancer (23.5 degrees north latitude). Therefore, the Northern Hemisphere will experience its greatest amount of possible daylight on that date.

Last year’s summer solstice marked the earliest astronomical star