SEATTLE — High temperatures will linger in the low 90s through at least Wednesday as the western Washington heat wave continues.
Favored locations to see high temperatures in the 90s will be areas away from water and regions south of Seattle along with the Cascade foothills and valleys. The Cascade valleys, Southwest Interior, including southern Mason County, could approach triple-digit heat this upcoming week.
Seattle is forecast to be on either side of 90 much of the week, and hit its third 90-degree day of the year on Tuesday.
Tuesday was also the hottest day of the year so far in Seattle, with the high temperature reaching 95 degrees.
Prior to the heat wave, Seattle-Tacoma International Airport recorded two days of high temperatures of 90 degrees or warmer. Back on July 5 and July 15, Seattle saw a high temperature of 91 degrees.
Seattle typically sees around three days of highs 90 degrees or warmer each year although that's been increasing over the past decade.
Overnight lows are forecast to remain mild during this heatwave, increasing the risk for heat-related illness as there will be little time for bodies and homes to cool. Lows will remain in the mid to upper 60s in Seattle and other areas with a high density of paved surfaces as these surfaces and environments hold in the heat from the afternoon sun.
The heat wave developed with a strong high pressure controlling the weather pattern for much of the upcoming week. This high pressure developed over the eastern Pacific over the weekend and is building across the West Coast, locking in place, and causing the extended stretch of high temperatures running 10-20 degrees above normal with low temperatures running 5-10 degrees above normal.
There's an Excessive Heat Warning in effect for the Seattle-Bellevue area through Wednesday night, signaling a major risk for heat-related illnesses.
The fire danger will be elevated this week due to the ongoing drought conditions, high temperatures, low relative humidity, and light offshore winds. These environmental and atmospheric conditions will favor the development and spread of wildfires.
Seattle has experienced a long stretch of mild high temperatures. The Emerald City is currently within a 55-day streak of high temperatures of 70 degrees or warmer. This ties 1981 for the fifth-longest streak, and there's no end in sight. The longest stretch is 72 days back in 2017.
A big reason for high temperatures staying above 70 degrees over the past two months is because of the summer season and abnormally warm water temperatures off the Washington coast. Water temperatures are running 1.5 to 2.5 degrees above normal. This helps lessen the cooling effect of onshore winds, thus, keeping Seattle in the lower 70s for highs during an onshore flow instead of the upper 60s.