Why the First Day of Summer Is the Longest Day of the Year

After months of long, grueling, cold and dark winter days, there's nothing more welcoming than the hours of sun that come along with the summer solstice each year.

The first day of summer typically arrives each year between June 20 and June 22, and this year, summer in the Northern Hemisphere will officially start on Wednesday. The season's arrival will bring forth the longest day of the year, which will result in some areas of the U.S. seeing the most amount of sunshine throughout the day.

During the June solstice, the Earth's tilt toward the sun is at its maximum, which causes the sun to appear at its highest elevation at 23.5 degrees latitude north directly over the Tropic of Cancer, according to the National Weather Service. Anywhere on the globe that is located north of the Tropic of Cancer—which runs through Mexico, the Bahama, Egypt, Saudi Arabia and southern China—will see the sun at its highest point for the longest amount of time, causing the June solstice to be the longest day of the year.

In laments terms, as the Earth spins on its axis, the Northern Hemisphere is faced directly toward the sun, exposing the region to the most sunlight the area will see during the year.

Although the exact amount of daylight an area will receive all depends on the Earth's latitudinal tilt toward the sun, most areas of the continental U.S. will see between 14 to 16 hours of sunlight. However, during the first day of summer, places far north like Alaska can see as many as 22 hours of sunlight.

In most places, the sun reaches its highest point above the horizon around noon.

The amount of daylight the Northern Hemisphere will receive will start to reduce following the solstice, but in its absence usually comes some of the hottest days of the year. This happens because the region holds on to heat for several weeks after the solstice, even though the Northern Hemisphere is starting to tilt further away from the sun as the Earth continues to rotate on its axis.

Oceans, in general, take longer to heat up than land, and once warm, the large bodies of water also play a significant role in maintaining seasonal temperatures.

As the season continues, the Northern Hemisphere starts to lose solar energy as the region receives less exposure to the sun—conversely the Southern Hemisphere starts tilting closer towards the sun—resulting in dropping temperatures.