Break out your sunscreen and sunglasses: Summer starts tomorrow.
Summer officially arrives with Wednesday's solstice. This time also marks the beginning of astronomical summer in the Northern Hemisphere.
So what is the summer solstice, exactly?
It's when the sun is at its highest point in the sky, directly above the Tropic of Cancer. This year, that occurs at 12:24 a.m. ET Wednesday. With the sun so high, it is also the longest day of the year for every place north of the Tropic of Cancer.
The solstice also brings the year's northernmost sunrise and sunset.
(Meteorologists consider summer to be the hottest three months of the year — June, July and August — which in terms of weather for those of us down here on Earth is more realistic than mid-June to mid-September.)
Washington, D.C., for example, will be watching the sunset at 8:37 p.m. ET after almost 15 hours of daylight and nine hours of darkness. Some areas north of the Arctic Circle will experience a natural phenomenon known as the midnight sun, where the sun remains visible for the full 24 hours.
For the next few days, the amount of daylight will stay about that length; then it will slowly start shrinking each day until the winter solstice on Dec. 21.
Also Wednesday: It's the winter solstice in the Southern Hemisphere, meaning it's going to start getting colder for the folks who live there.
Many people around the world celebrate the summer solstice with music and festivities. In England, hundreds will travel at the ancient site of Stonehenge to celebrate the first day of summer.
Next year, the solstice will be on June 21.
In the U.S., a large and persistent high-pressure system is scorching parts of California, Nevada, Arizona and New Mexico. Some areas could hit as high as 120 degrees, forecasters said.
Contributing: Doyle Rice, USA TODAY