Summer Solstice Saturday: Longest Day And Shortest Night Of The Year

When it’s still dusk at 9 or 10 p.m. and gets light again around 5 o’clock the next morning, we know the longest day of the year is upon us. This Saturday is the June solstice, marking the longest day of the year and the astronomical start to summer in Earth’s northern hemisphere.

At 6:51 a.m. EDT on June 21, the sun can be seen directly overhead along the Tropic of Cancer at 23.5º north latitude. With the Earth’s North Pole at its maximum tilt toward the sun, locations north of the equator see the sun follow its longest and highest path across the southern sky. This means the shadow you cast at local solar noon will be the shortest of the year.

The exact amount of daylight we see on the summer solstice is highly dependent on latitude (see image). North of the Arctic Circle, the sun circles the sky for 24 hours. But while the high latitudes see continuous daylight, the sun’s low angle in the sky provides very ineffective heating. As a result, temperatures in the Arctic aren’t exactly summerlike even when the sun is up for weeks or months at a time.

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