Thursday's solstice brings summer -- and then the days start to get shorter

Summer arrives at 5:07 a.m. Thursday to usher in a season of indoor-outdoor, shoes-optional breezy living.

And then darkness begins to descend.

It always has seemed a little unfair that the solstice that marks summer's onset also signals a reversal: the gradual increase in daylight that has been a saving grace since Dec. 21 begins to head in the other direction.

On Friday, daylight in Chicago will last three seconds shorter than on Thursday, the longest period of daylight in the year, reports timeanddate.com.

Our seasonal swing

By July 21, daylight will last 1 minute and 42 seconds shorter. And so it goes, until the 15 hours, 13 minutes and 34 seconds of daylight on Thursday become the 9 hours, 7 minutes and 46 seconds of daylight on Dec. 21.

It's all because of Earth's tilt. When Earth's orbit places the northern hemisphere tilting toward the sun, it's summer in our region, says the Smithsonian Science Education Center. When the tilt is away from the sun, it's winter.

If you live closer to the North or South poles, the difference in daylight is more pronounced.

More sunlight than Miami

We have a leg up on the Sunshine State this time of year, as Miami gets 13 hours, 44 minutes and 58 seconds of daylight on Thursday, its longest day. Bellingham, Washington, the continental U.S.'s northernmost big city, gets 16 hours, 9 minutes and 41 seconds of daylight on Thursday. In Barrow, Alaska, the sun won't set at all in June.

So go get an ice cream because summer is fleeting, beginning on its very first day.