The exact dates each season begins in 2026, why they fall when they do, and the difference between the astronomical seasons that follow the Sun and the meteorological ones that follow the calendar.
In 2026, the Northern Hemisphere seasons begin on:
Spring — 20 March · Summer — 21 June · Autumn — 23 September · Winter — 21 December. South of the equator the same four dates start autumn, winter, spring and summer instead.
The 2026 season dates
Each astronomical season starts at a precise instant — an equinox or a solstice — that happens at the same moment everywhere on Earth, even though the local calendar date can differ by a day depending on your time zone. The times below are in UTC; the date names are for the Northern Hemisphere.
Season starts
Date (2026)
Event
Spring
20 March, ~14:46
March equinox
Summer
21 June, ~08:25
June solstice (longest day)
Autumn
23 September, ~00:05
September equinox
Winter
21 December, ~20:50
December solstice (shortest day)
In the Southern Hemisphere the seasons are reversed: the June solstice begins winter and the December solstice begins summer. Because the moment is fixed in UTC, places far to the east or west can see the equinox or solstice land on the day before or after the dates above.
Equinox vs solstice — what's actually happening
The seasons exist because the Earth's axis is tilted about 23.4° as it orbits the Sun. Through the year that tilt points the Northern Hemisphere first toward the Sun, then away, and the four turning points are the equinoxes and solstices.
An equinox is when the Sun sits directly over the equator, so day and night are close to equal length everywhere — the word means "equal night." The March equinox starts spring; the September equinox starts autumn.
A solstice is when the Sun reaches its highest or lowest point in the midday sky, giving the year's longest or shortest day. The June solstice (longest day in the north) starts summer; the December solstice (shortest day) starts winter.
Between an equinox and the next solstice the days are getting longer or shorter fastest around the equinox, and barely changing at all around the solstice — which is why "solstice" comes from Latin for "Sun stands still."
Astronomical vs meteorological seasons
There are two common ways to mark the seasons, and they start on different dates:
Astronomical seasons follow the Sun, starting at the equinoxes and solstices above. Their start dates wobble by a day or two each year and the seasons aren't all the same length.
Meteorological seasons follow the calendar, each running three whole months. This is what weather services use because tidy months are far easier to compare from one year to the next.
The meteorological seasons in the Northern Hemisphere are:
Season
Months
Starts
Spring
March · April · May
1 March
Summer
June · July · August
1 June
Autumn
September · October · November
1 September
Winter
December · January · February
1 December
So depending on which definition you use, "the first day of summer" is either 1 June or around 21 June. Both are correct — they just answer slightly different questions.
Why the dates shift a little every year
A full orbit of the Sun takes about 365.25 days, not a round 365. That extra quarter-day means each equinox and solstice happens roughly six hours later than it did the year before, nudging the calendar date forward. Then a leap day every four years adds a whole day back to February, which resets the drift and pulls the dates earlier again.
The result is a gentle wobble: the March equinox, for example, lands somewhere around the 19th to 21st, never on a fixed date. Over very long spans the leap-year rules keep this in check so the seasons don't slowly slide through the calendar — the same reason the calendar year stays locked to the seasons at all.
Why the hottest weather comes after the longest day
It feels backwards that summer's longest day is in June yet the warmest weeks usually come in July or August. The reason is thermal lag: even after daylight starts shrinking, the Sun is still delivering more heat than the land and oceans give back, so temperatures keep climbing for weeks after the solstice. The same lag at the other end of the year is why the coldest weather trails the December solstice. The Sun sets the schedule; the planet takes its time catching up.
Related calendar tools
To count the days until the next equinox or solstice, use the days-until countdown; to see the whole year laid out with week numbers, open the 2026 week calendar; and for why the dates drift in the first place, see is 2026 a leap year?
Both, depending on the system. Meteorologists count summer as June, July and August, so it starts on 1 June. The astronomical season tied to the Sun starts at the June solstice, around 21 June. News and weather reports often mean the meteorological date; almanacs and astronomers mean the solstice.
Why are the seasons opposite in Australia?
Because the Earth's tilt points one hemisphere toward the Sun while the other points away. When the Northern Hemisphere leans into the Sun for its summer, the Southern Hemisphere is leaning away and having winter. The equinoxes and solstices happen at the same instant worldwide — they just begin opposite seasons north and south of the equator.
Are day and night exactly equal on the equinox?
Almost, but not perfectly. The Sun is a disc rather than a point and the atmosphere bends its light, so sunrise comes a touch early and sunset a touch late. That tips the balance toward daylight by a few minutes on the equinox itself; the true 12-hour day falls a day or two on either side, an event called the equilux.
When is the longest day of the year?
In the Northern Hemisphere it's the June solstice — 21 June 2026 — when the Sun climbs highest and daylight lasts longest. The shortest day is the December solstice on 21 December 2026. South of the equator the two swap over.
Season start times are astronomical figures for the year 2026 and are given in UTC; your local date may differ by a day. This page is fixed reference material — nothing you read here is sent anywhere.