Originally published August 9, 2012 at 9:01 PM | Page modified August 10, 2012 at 6:41 AM
Sorry, but summer is almost outta here
Historic weather readings in Seattle indicate that by the end of next week, we'll be heading into the end of summer.
Seattle Times staff reporter
ERIKA SCHULTZ / THE SEATTLE TIMES
Sam Hanson, 10, plays baseball with a friend at Golden Gardens Park in Seattle on Thursday as warm weather returns to the region a week after a record-setting heat wave. But "things are slowly changing" to a cooler trend, says a local weather expert.
With temperatures forecast in the upper 70s Friday and into the 80s for the weekend, it's time to soak up some sunshine, toss a Frisbee and grill up some burgers.
And do it now: We're approaching the time of year when, temperaturewise, summer begins to end.
"Things are slowly changing," said Dennis D'Amico of the National Weather Service, "and that change will gradually accelerate."
Consider the numbers: At Seattle-Tacoma International Airport, where the city's official readings are taken, the normal high temperature for today's date is 77 degrees.
That's been the normal high each day since July 19, and will continue to be the case through next Thursday — a total of 29 days.
But starting next Friday, the normal high at Sea-Tac drops to 76, then it drops again a week later to 75.
And by Sept. 22, when summer technically does end, Sea-Tac's normal high will be down to 69, and dropping every few days.
So who decides what's normal? D'Amico said it's based on an average of readings taken over a 30-year period, 1981 through 2010.
Although most summers include a heat wave or two, such as the one that produced 93-degree days at Sea-Tac last weekend, averaging readings over three decades smooths out peaks and valleys.
Since summer officially began June 20, the daily high at Sea-Tac has been above normal 18 times, below normal 30 times, and equal to the normal reading three times.
The readings confirm what all those back-to-school ads have been suggesting — that Seattle's summer, notoriously late in arriving, doesn't stick around long.
As fall approaches and the minutes of daylight decrease daily, D'Amico said, the sun has less time to heat things up.
But that doesn't mean that minutes of daylight automatically translate into hot weather. The longest day of the year comes at the start of summer. In the late spring and early summer, D'Amico said, more moist air is moving in from the Pacific Ocean, tending to keep the Puget Sound area cool and cloudy.
Travelers to Eastern Washington should expect a continued blast of summer, with temperatures this weekend into the high 90s and near 100.
Jack Broom: 206-464-2222 or jbroom@seattletimes.com
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