Summer Dates Table
| Aspect | Meteorological | Astronomical |
|---|---|---|
| Starts | June 1, every year | Solstice, June 20-21 |
| Ends | August 31, every year | Equinox, Sep 21-23 |
| Length | always 92 days | a few days longer |
| Basis | calendar quarters | Earth tilt and orbit |
| Used by | NOAA records, insurers | almanacs, sky calendars |
Summer has two official starting guns. The meteorological calendar opens it on June 1 and closes it August 31 - the same three months every year, so records and forecasts compare like with like. The astronomical calendar waits for the solstice, near June 20-21, and runs to the September equinox, near the 21st to 23rd. The table and the counter below give you both calendars for any year you type.
Why two calendars? NOAA's National Centers for Environmental Information put it plainly: meteorological seasons chop the year into tidy quarters that follow the annual temperature cycle, which is what forecasters and statisticians need; astronomical seasons track the tilt of Earth's axis through its orbit, which is what almanacs and sky calendars need. Same sunshine, different bookkeeping - and in the Southern Hemisphere the whole thing flips to December through February.
How to use
- Type a year between 2024 and 2036 - the counter reads back the days until (or left of) meteorological summer, plus the weekdays June 1 and August 31 land on.
- Read the comparison table before you plan: meteorological summer is always exactly 92 days - June 30, plus July 31, plus August 31 - which is why agencies schedule against it.
- Treat the astronomical start as a window, not a date: the solstice lands June 20 or 21 depending on the year and your time zone, so check an almanac if the exact day matters.
Frequently asked questions
Is June 21 always the first day of summer?
Only on the astronomical calendar, and even then it slips: the solstice lands on June 20 in some years and June 21 in others, and a leap year can nudge it again. Meteorological summer ignores all of that and starts June 1, every year - which is exactly why the dates on this page hold still.
Why does meteorological summer start on June 1?
Because weather services need seasons that compare cleanly. Fixed calendar quarters follow the annual temperature cycle, so a June-through-August average means the same thing every year; NCEI, NOAA's archive arm, keeps its climate records on that basis and publishes the meteorological-versus-astronomical explainer cited below.
When does summer start in Australia?
It flips. South of the equator, meteorological summer runs December 1 to the end of February, and the astronomical summer solstice there falls in late December. A July beach day in Sydney is a winter day - the definitions follow the hemisphere, not the month.
How long is summer, exactly?
Meteorological summer is always 92 days: June 30, July 31, August 31. Astronomical summer in the Northern Hemisphere runs a few days longer than that and is the longest season of the year - Earth passes its farthest point from the sun in early July and moves slowest there, so the season stretches.