Sunday was darkest June day in Seattle in 15 years

The day before the summer solstice — when the sun's rays should shine strongest over the Northern Hemisphere — might instead have been "the darkest June day anyone's ever experienced" in Seattle, said Cliff Mass, professor of atmospheric sciences at the University of Washington.

Sunday was the darkest June day on record for the area in at least 15 years, but Mass said it's likely been much longer.

The darkness, measured as solar radiation from the roof of the UW atmospheric-sciences building, was more fitting for an early February day, he said.

"It was extraordinary," Mass said of Sunday's distinctly un-summerlike weather. "It wasn't an earthquake or a tornado, but it's very unusual and it's worth noting."

And missing along with the sun's brightness is the summer warmth it brings.

Seattle is on a stretch of 271 days and counting without reaching 75 degrees, said Dennis D'Amico, a meteorologist with the National Weather Service. The previous record was 254 days.

"We have crushed that," Mass said, adding it's likely temperatures won't reach 75 until July.

It's not just that it's not warm — it's been far colder than June's usual high of 70.

At 56 degrees, Sunday's high was just 1 degree above the lowest high ever recorded at Seattle-Tacoma International Airport on a June 20. That's a typical mid-April high.

Monday, the sun came out at times, and Seattle hit a high of 63.

Mass attributes the cool weather to a trough of low pressure overhead. He noted the drastic difference between this year and last, when the Seattle area experienced one of its driest and warmest springs.

So far, this June has been the eighth wettest on record, with 2.49 inches.

D'Amico predicts it will break into the top five; the record is 3.82 inches, set in 1964. More rain is expected this weekend.

"Even for me, a lover of rain and clouds," Mass wrote on his weather-tracking blog, "this is going too far."

Carly Flandro: 206-464-2108 or cflandro@seattletimes.com