The summer solstice is the day with the most daylight of the year, when your part of Earth gets more daylight than any other day. In the Northern Hemisphere (which includes the United States, Europe, and most of Asia), this happens around June 20 or 21. In the Southern Hemisphere (including Australia, South America, and southern Africa), it occurs around December 21 or 22.

On the summer solstice, the sun reaches its highest point in the sky at noon and stays up longer than on any other day. If you live far north, like in Alaska or Scandinavia, the sun barely sets at all: you might have sunlight until nearly midnight. The farther north you go, the more extreme this effect becomes. At the Arctic Circle, the sun doesn't set for a full 24 hours.

For a few days around the solstice, the sun seems to pause at its highest point before reversing direction. After the summer solstice, days gradually get shorter until the winter solstice six months later.

Many cultures throughout history have celebrated the summer solstice with festivals, bonfires, and gatherings. Ancient people built monuments like Stonehenge in England to mark this important astronomical event. Today, people still often celebrate it as the beginning of summer.