Last July wasn’t even this warm.
The mercury at Sea-Tac Airport shot up to 84 degrees today—a temperature not reached in Seattle last year until Aug. 4., when summer was already halfway over. The near-record May heat—the city barely missed out on the all-time high for the day of 86—also gave Seattle its earliest 80-degree reading since 2004, when the temperature cracked 80 on April 11.
The scorching temperatures are due to the combination of a strong ridge of high pressure overhead and a very warm area of low pressure at the surface—better known as a thermal trough. The thermal trough, which has been parked along the Washington coast since the weekend began, is the result of easterly winds blowing down the Cascades into Western Washington. Because air warms as it sinks, these winds are able to funnel hot air westward into the region—baking the Sound in summer-like heat. (Hot air is also less dense than cold air, which is why it’s called a thermal trough—or low.)
With the setup remaining the same tomorrow, we’ll visit the 80s once again as high temperatures level off close to today’s readings. This should allow Seattle to easily smash Monday’s record high of 79 degrees, logged back in 1957.
Cooler air finally trickles in early Tuesday as the thermal through heads into the Cascades, dropping maximum temperatures back to near 70 degrees. While that’s still rather warm for early May, it’s at least in the same ballpark as the average high of 63—unlike the staggering 20-degrees-above-normal readings we saw today. In addition, gray skies are likely Tuesday morning south of Seattle as the winds reverse course, dragging a band of low clouds in from the ocean and up through the Chehalis Gap.
Thermometers rise into the mid 70s again by Wednesday as high pressure strengthens overhead, although the morning should feature plenty of clouds as well. We’ll ditch the cloudcover completely by Thursday, sending temperatures soaring back into the upper 70s under blazing blue skies.
At this point, Seattle looks to warm even further on Friday and Saturday—think 80 degrees again—before a cold front brings back the raindrops next Sunday.
And summer finally yields to spring.
