Oh sure, you scoff now. Summer’s hardly started, you say. But Seattle has already seen its last 9 p.m. sunset of the year and as of Saturday will have lost an hour of light since the summer solstice.

“We won’t see that again until next Memorial Day,” said Justin Shaw of Seattle Weather Blog.

“I always feel that’s a preliminary marker of the Big Dark and soon we begin our slow descent into darkness,” Shaw said.

At our latitude of 47.6 degrees, Seattle feels both extremes of the solstices more than nearly any other city in the Lower 48, with 16 hours of daylight and two hours of nautical twilight on our longest day and only eight hours of light on Dec. 21.

By next month, we will have seen our last 8 p.m. sunset of the year. Then, the loss of daylight and twilight — when the sun is below the horizon but there’s still light — will accelerate.

The amount of daylight and twilight Washington gets doesn’t increase or decrease at a steady pace from one day to the next, either. Rather, it changes slowly near the solstices in December and June and quickly near the equinoxes in March and September.

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It’s easy for most new people to overlook how that affects daily lives here. A midwinter day in Everett is about 8 hours and 20 minutes. In Phoenix, it’s almost 10 hours; in Miami, 10½.

“In California, and other places, where the days and nights don’t fluctuate so much, it’s not that big of a deal,” said Shaw, “but here we are descending down a mountain and picking up speed as we go.”

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What does it mean for Washingtonians? During midwinter in the state’s most northern towns, “the ‘3:30 rule’ is widely in effect: If you don’t get your stuff together in time to walk your dog, prune the dogwoods or mend the fence by 3:30 p.m., you’re going to be finishing in the dark,” Seattle Times staff writer Ron Judd said in 2015.

So yes, summer is still here and it’s still light out at night, but the inevitable has begun. It’s time to make the most of the summer, which is as fleeting as always.