SUNDAY EVENING: A few shower will roll north across the Puget Sound lowlands mainly south of Everett this evening while lightning-producing thunderstorms rumble through the Cascades. A Red Flag Warning for high fire danger is in effect east of the Cascade crest. West of the crest, moisture levels in the west slopes of the Cascades is high enough that the fire danger isn't high enough to produce a warning.
Lowland showers will be sporadic through the evening, diminishing before midnight. Storms in the mountains and on the east slopes of the Cascades will continue through the night.
A Heat Advisory is in effect for Western Washington through Monday morning as high temperatures Sunday will again be in the 80s and lower 90s.
It'll be another hot day across most of Western Washington, save for the coast and islands of the north where clouds and cool water will keep temperatures down into the 60s and 70s. Elsewhere, expect 80s to around 90.
A disturbance moving northeast toward the Pacific Northwest will interact with the hot air and humidity to spark showers and thunderstorms over the mountains later today, starting in the south near the Oregon border and then moving north.
While the greatest lightning threat will be in the mountains late today, the lowlands also have a chance of lightning mainly after 4 p.m. today lasting into the evening.
Rainfall amounts will be light or nil with these thunderstorms as the cloud bases will be very high off the ground. Much of the rain will evaporate before reaching the surface. However, numerous lightning strikes will be possible.
Thunderstorm chances fade after dark.
Monday morning will feature a few more clouds with slightly cooler afternoon temperatures -- in the 80s.
We'll ramp temperatures back up to the upper 80s and lower 90s in Seattle Tuesday and Wednesday before cooler temperatures arrive by Thursday.
Sunday 91° 93° (1961)
Monday 87° 91° (1996)
Tuesday 92° 92° (1958)
At this point, we’re looking to break out of this heat wave around Thursday. A trough of low pressure moves into our area, bringing in some cooler air. High temperatures fall back into the 80s and 70s for the following weekend.