How Many Days Until Summer?

There are two common answers. Astronomical summer begins at the June solstice — the instant the Sun reaches its northernmost point in the sky — which lands on June 20 or 21 (and very rarely June 22) depending on the year and your time zone. Meteorological summer, used by weather agencies because it makes cleaner statistics, simply runs June 1 through August 31. This countdown follows the astronomical definition and uses June 20 as its target date.

The solstice wobbles between dates because the calendar year (365 or 366 days) never exactly matches the astronomical year of about 365.2422 days. Each year the solstice moment drifts roughly six hours later, then leap years pull it back. In the 2020s and beyond it most often falls on June 20 in US time zones, which is why that date anchors the counter.

The June solstice is the moment Earth's North Pole tilts most directly toward the Sun, putting the Sun straight overhead at the Tropic of Cancer. For the Northern Hemisphere it delivers the year's longest day and shortest night — the farther north you are, the more extreme, up to the midnight sun above the Arctic Circle. The word itself comes from the Latin solstitium, "the Sun stands still," because the Sun's daily path stops drifting north and reverses.

Humans have marked the moment for millennia: Stonehenge aligns with the solstice sunrise, and midsummer festivals remain major holidays in Scandinavia. One quirk worth knowing — the solstice is the longest day, but thanks to seasonal lag the hottest weather usually arrives weeks later in July, and in the Southern Hemisphere this same moment marks the start of winter.