The seasons

Seasons come from Earth’s tilt, not its distance from the Sun. Earth is closest to the Sun in early January, in the middle of the northern winter, which surprises nearly everyone up north.

The tilt

Earth’s axis leans 23.4° from upright. For half the year the Northern Hemisphere leans toward the Sun: the Sun climbs higher, days run longer, and sunlight strikes the ground more directly. For the other half the Southern Hemisphere does. The solstices mark the strongest lean each way, and the equinoxes the two moments in between, when the Sun stands over the equator.

How long each season lasts in 2026

North	South	Starts	Length
Spring	Autumn	Mar 20	92 d 17 h 39 min
Summer	Winter	Jun 21	93 d 15 h 41 min
Autumn	Spring	Sep 23	89 d 20 h 45 min
Winter	Summer	Dec 21	88 d 23 h 34 min

The seasons are not equal. Earth moves fastest near perihelion in January and slowest near aphelion in July, so it hurries through the northern winter and lingers through the northern summer: about 4.7 days’ difference. See the time between any two moments.

Three ways to count

	Northern spring	Northern summer
AstronomicalSeasons start at the solstices and equinoxes.	Mar 20 to Jun 21	Jun 21 to Sep 23
MeteorologicalWhole months, for weather records.	Mar 1 to May 31	Jun 1 to Aug 31
TraditionalSeasons start at the cross-quarter days, so the solstices fall at midsummer and midwinter. Solmanac’s Evensun names follow this one.	Feb 3 to May 5	May 5 to Aug 7

Two centuries of change

Perihelion slowly moves later in the year, about a day every 58 years, so the fast part of the orbit shifts from winter toward spring. Over two centuries northern spring and winter shorten by a few hours, and summer and autumn lengthen to match.

Year	Spring	Summer	Autumn	Winter
1900	92.83 d	93.61 d	89.76 d	89.03 d
1950	92.79 d	93.63 d	89.81 d	89.01 d
2000	92.76 d	93.65 d	89.84 d	89.00 d
2050	92.72 d	93.66 d	89.88 d	88.97 d
2100	92.69 d	93.69 d	89.91 d	88.96 d

Northern names; lengths in days, from each season’s start to the next.