First up, the date today seemed familiar to be for weather significance, and sure enough I was right. Step outside today, and many areas were in the 70s (with North Bend actually nearing shouting distance of 80).
Two years ago today? It snowed! And not just a little, some spots in southern Snohomish County had between 3-7" (Clearview had 10"!) as a roaring convergence zone raged. It was one of the latest big snows ever in the general sense. Officially for Seattle, the latest official snow is April 17, and although it did snow just a touch at Sea-Tac on April 19, 2008, it wasn't enough to measure, so April 17 still holds for the Emerald City.
But even here in 2010, where the pattern is the complete opposite and we're dealing with near-record highs, there is still quite a bit of variance. At 11 a.m., the temperature was 70 degrees in Everett and Arlington; 73 in Redmond and 70 in North Bend. But check out some of these other temperatures at the same time: Bellingham 66, Eastsound (Orcas Isl.): 55, Port Angeles 57, Seattle (Boeing Field) 64, Sea-Tac Airport 58, Gig Harbor 57, Bremerton 64 and Chehalis 59, but that zoomed to 63 40 minutes later.
So that's almost a 20 degree spread across the region.
We became a bit more uniform as we headed into the afternoon with temperatures pretty much 65-72.
The "heat wave" is being caused by easterly winds being drawn toward a stalled cold front offshore. As those winds sink down the Cascades, they compress and heat further, which is why it's really toasty over on the Eastside. (North Bend was at 76 as of 1 p.m.) The heat will come to an abrupt end once the front finally staggers ashore tonight.