Winter 2026 starts twice in the Northern Hemisphere. Meteorological winter begins on Tuesday, December 1, 2026. Astronomical winter begins at the December solstice, on Monday, December 21, 2026 at 20:50 UTC, which is 3:50 p.m. Eastern and 12:50 p.m. Pacific. Both answers are correct. They come from two different systems built to answer two different questions, and the three weeks between them are one of the most reliable sources of seasonal confusion every year.
Astronomical winter begins at an instant, not on a date
The astronomical seasons are defined by Earth’s position relative to the Sun. Winter begins at the December solstice, the moment the Sun reaches its southernmost point in the sky and stands directly over the Tropic of Capricorn. It ends at the March equinox, when the Sun crosses the celestial equator heading north. The mechanics of both turning points are covered in our guide to the equinox and solstice.
Because the solstice is a single moment, the calendar date depends on where you are. The 2026 solstice at 20:50 UTC falls on December 21 across the Americas, Europe and Africa: 8:50 p.m. in London, 9:50 p.m. in Berlin. In East Asia and Australia it is already December 22: 4:50 a.m. in Beijing, 5:50 a.m. in Tokyo and 7:50 a.m. in Sydney. The solstice also moves from year to year, because the calendar year and the solar year don’t match exactly. In UTC, the December solstice falls on December 21 or 22 in most years; in 2027 it lands on December 22 in UTC while still falling on the evening of December 21 in US time zones.
The solstice brings the shortest day of the year north of the equator. The name describes what the Sun appears to do: its slide southward along the horizon slows, pauses and reverses, as if it stood still. The word comes from Latin sol, sun, and sistere, to stand still. For the same reason, day length changes only by seconds in the days on either side of the solstice.
Meteorological winter runs on whole months
Meteorologists and climatologists divide the year into four blocks of three full months. According to NOAA’s National Centers for Environmental Information, meteorological winter in the Northern Hemisphere is December, January and February; spring is March through May; summer is June through August; and fall is September through November.
The reason is practical. Weather records are kept by day and month, and a season that starts on the 1st lines up with monthly statistics. The NCEI notes that this makes seasonal averages much easier to calculate and compare, and that meteorological seasons vary less in length: from 90 days for winter in a common year to 92 days for spring and summer. Winter 2026-27 runs from December 1 to February 28, exactly 90 days. The following winter picks up an extra day, because February 2028 has 29 days in a leap year, making it 91 days long.
The meteorological grouping also tracks the temperature cycle more closely. In the Northern Hemisphere’s mid-latitudes, the coldest three-month stretch typically begins in late November or early December and runs through late February or early March. The astronomical definition, by contrast, leaves the first three weeks of December in autumn and counts the first three weeks of March as winter.
| Definition | Winter 2026-27 begins | Winter ends | Length |
|---|---|---|---|
| Astronomical (Northern Hemisphere) | December 21, 2026, 20:50 UTC | March 20, 2027, 20:25 UTC | About 88 days 23.6 hours |
| Meteorological (NOAA and many weather services) | December 1, 2026 | February 28, 2027 | 90 days |
| Thermal (Sweden’s SMHI) | First of five days in a row with a daily mean of 0.0°C or lower | Varies by location | Varies, and can be zero |
| Traditional Irish (Celtic) | November 1 | January 31 | 92 days |
Why the coldest days come weeks after the solstice
If the solstice gives the least sunlight, why isn’t it the coldest day? Because land and especially oceans store heat. After the solstice, the Northern Hemisphere still loses more energy each day than it gains, and temperatures keep falling until incoming sunlight catches up. This delay is called seasonal lag.
NOAA’s “Coldest Day of the Year” maps show how large the lag is. The version built on the 1981-2010 Climate Normals found that the western half of the Lower 48 typically reaches its coldest day in December, while most eastern stations bottom out in January. The update based on 1991-2020 normals shows Alaska typically coldest in January, while Hawaii and Puerto Rico can have their coldest days in February or even early March. Compared with the earlier map, NCEI found that the coldest day had shifted 3 to 6 days later or more at many US stations.
Light plays tricks around the solstice too. At mid-northern latitudes, the earliest sunset of the year comes in early December, about two weeks before the solstice, and the latest sunrise comes in early January. The shortest day sits between them. The asymmetry comes from the equation of time: in December, solar noon drifts later on the clock by about 30 seconds a day, pulling both sunrise and sunset later even while total daylight is still shrinking.
Astronomical winter is the shortest season of the year
The four astronomical seasons are not equal in length, and winter comes out shortest. Earth’s orbit is slightly elliptical, and Earth reaches perihelion, its closest point to the Sun, in early January: on January 3 in 2027. By Kepler’s second law, a planet moves fastest near perihelion, so Earth covers the quarter of its orbit from the December solstice to the March equinox in less time than any other quarter.
Northern Hemisphere winter is the shortest astronomical season because Earth moves fastest along its orbit in early January, when it is closest to the Sun. worldtimedata
The 2026-27 numbers make the difference concrete. Astronomical summer 2026, from the June solstice (June 21, 08:25 UTC) to the September equinox (September 23, 00:06 UTC), lasted about 93 days 15.7 hours. Astronomical winter 2026-27, from December 21, 20:50 UTC to March 20, 2027, 20:25 UTC, lasts about 88 days 23.6 hours. That is a gap of more than four and a half days, calculated from the published solstice and equinox times.
Being closer to the Sun in January doesn’t make northern winters warm. The distance changes by only about 3% over the year, while the tilt of Earth’s axis controls how high the Sun climbs and how long it stays up, and that effect is far larger.
Places where temperature decides
Some countries skip fixed dates entirely. Sweden’s meteorological institute, SMHI, defines winter by temperature: winter has arrived at a location once the daily mean temperature has been 0.0°C or lower for five days in a row, and the first of those five days counts as the start. Under that rule, winter reaches northern Lapland months before southern Sweden, and SMHI notes that several stations in the far south have no winter at all on average. In 2025, Gothenburg’s station met the definition only in mid-February, and some nearby stations still hadn’t.
Older calendars put the season in a different place again. In the traditional Irish calendar, winter begins on November 1 and runs through January, which centers the season on the solstice rather than starting it there. That older logic survives in English, where the solstice was traditionally called Midwinter. The modern astronomical convention puts the same moment at the very beginning of the season instead.
In the Southern Hemisphere, winter starts in June
South of the equator, everything shifts by six months. Meteorological winter runs from June 1 to August 31, and that is the convention most commonly used in Australia and New Zealand. Astronomical winter there begins at the June solstice, which in 2027 falls on June 21 at 14:10 UTC, or 12:10 a.m. on June 22 in Sydney. The same December 2026 solstice that opens winter in New York opens astronomical summer in Sydney, on the morning of December 22 local time.
