Seasons 2026 and 2027: equinox and solstice dates

When do the seasons start?

Astronomers mark four turning points in the Sun's year. At the equinoxes, around March 20 and September 22 or 23, the Sun crosses the celestial equator and day and night are nearly equal everywhere. At the solstices, around June 21 and December 21 or 22, the Sun reaches its farthest point north or south and the days are longest or shortest. Each of them is an exact instant, calculated from the Sun's position along the ecliptic: 0, 90, 180 and 270 degrees.

First day of winter

The winter solstice, December 21, starts astronomical winter in the Northern Hemisphere. It is the shortest day of the year. Read more on the winter solstice 2026 page, with day length for 38 cities.

First day of spring

The March or vernal equinox, March 20, starts astronomical spring. The Sun rises due east and sets due west, and the days grow fastest. Persian New Year, Nowruz, begins at this moment. See the spring equinox 2027.

First day of summer

The June solstice, June 21, starts astronomical summer, with the longest day and the highest noon Sun of the year. See the summer solstice 2027.

First day of fall

The September equinox, September 23, starts astronomical fall. From here the nights are longer than the days until March. The Harvest Moon is the full moon nearest to it. See the autumn equinox 2027.

Astronomical vs meteorological seasons

There are two ways to divide the year, and both are correct. Astronomical seasons follow the Sun: they start at the solstices and equinoxes, so the start dates move by a day or so from year to year and the seasons have different lengths. Meteorological seasons are tidy blocks of three whole months, chosen so that weather records can be compared month by month and year by year. National weather services such as NOAA and the UK Met Office use the meteorological seasons for their statistics.

What causes the seasons: the 23.4 degree tilt

Earth spins on an axis that is tilted about 23.44 degrees from upright compared with the plane of its orbit. (That figure is computed here as the Sun's farthest distance north of the celestial equator at the June solstice, which is exactly the tilt.) The axis keeps pointing the same way in space all year, close to Polaris, the North Star. So as Earth goes round the Sun, first one hemisphere and then the other leans towards it.

The hemisphere leaning towards the Sun gets two things at once. The Sun climbs higher in the sky, so its light strikes the ground more directly and each square metre receives more energy; and the Sun stays up longer, so there are more hours of heating than of cooling. That is summer. Six months later the same hemisphere leans away: low Sun, short days, winter. The diagram above shows the axis leaning the same way at all four points of the orbit, and the Sun path chart below shows what that does to the Sun's height in your own sky.

Distance is not the cause. Earth is closest to the Sun in early January, in the middle of the northern winter, and farthest in early July. If distance drove the seasons, both hemispheres would have summer at the same time.

Why the seasons are not the same length

Earth's orbit is very slightly oval, with an eccentricity of about 0.0167. At perihelion, on Sunday, January 3, 2027, Earth is 147.10 million km from the Sun. At aphelion, on Monday, July 5, 2027, it is 152.10 million km away, about 5.0 million km farther. Sunlight at perihelion is about 6.9% stronger than at aphelion, which slightly softens northern winters and sharpens southern summers.

By Kepler's second law, a planet moves fastest when it is nearest the Sun. Earth races through the part of its orbit around January and dawdles around July. The solstices and equinoxes are evenly spaced around the orbit, a quarter turn apart, but the time Earth takes to cover each quarter is not equal. These are the astronomical season lengths, calculated from the exact moments:

Northern summer is about 4.7 days longer than northern winter. The difference slowly changes over thousands of years, because the date of perihelion drifts through the calendar (about one day every 58 years) as the orbit and the axis both slowly turn.

Seasons in the Southern Hemisphere

In Australia, New Zealand, South Africa and South America everything is reversed. The December solstice is the start of summer and the longest day, the March equinox starts autumn, the June solstice starts winter, and the September equinox starts spring. Meteorological seasons are reversed too: southern summer is December, January and February. If you choose a southern city with the location button above, the pages on this site switch their wording to match.

Other ways to mark the year

Many calendars split the year more finely. The old Gaelic year began its seasons at the cross-quarter days halfway between the solstices and equinoxes: Samhain for winter, Imbolc for spring, Bealtaine for summer and Lughnasa for autumn. Modern Pagans combine all eight points in the Wheel of the Year. The traditional Chinese calendar divides the Sun's path into 24 solar terms, 15 degrees apart, including Dongzhi at the winter solstice and Chunfen at the spring equinox. Near the equator, where day length barely changes, seasons are usually wet and dry rather than warm and cold.