Spring 2026 in the Northern Hemisphere begins 2026-03-20. Summer begins 2026-06-21, autumn 2026-09-23, winter 2026-12-21. All times UTC, computed from Earth's orbit using Meeus's astronomical algorithms (±1 minute precision).
An equinox happens twice a year (around March 20 and September 22-23) when the Sun crosses Earth's equator. On those days, the day and night are roughly equal length everywhere on Earth.
A solstice happens twice a year (around June 21 and December 21) when the Sun reaches its furthest position north or south of the equator. The summer solstice is the longest day of the year; the winter solstice is the shortest.
These dates differ between the Northern and Southern Hemispheres — when the North experiences the summer solstice, the South experiences the winter solstice on the same astronomical moment.
Meteorologists define seasons by the calendar quarter — spring is March–May, summer is June–August, and so on, with seasons starting on the 1st of the month. This makes weather statistics easier to compute. Astronomical seasons (the ones above) shift slightly each year because Earth's orbit isn't exactly 365 days.