The 'Heat Dome' Arrives: 3 Extremely Hot Days Ahead In Washington

SEATTLE — An unprecedented heat wave is still on track for Washington and much of the Pacific Northwest, with temperatures poised to soar higher each day through Monday. The National Weather Service activated an excessive heat warning across Washington at 2 p.m. on Friday and it will remain in place until at least 9 p.m. Monday.

Afternoon temperatures are likely to hit triple digits for many on Sunday, and a few may get there by Saturday. Monday is forecast to be even hotter, with a chance some cities may log their hottest temperatures ever recorded.

"This is expected to be an unprecedented event," NWS Seattle wrote Friday. "Those of us at the office have never seen PNW forecast data like this. We encourage everyone to make plans now to check in on and ensure their loved-ones, neighbors, pets, and the entire community remain safe and healthy."

What is an excessive heat warning?

Regional National Weather Service offices issue an excessive heat warning when forecasters expect there will be a prolonged period of dangerously high temperatures, which are beyond a certain threshold on the heat index.

The warning in place for Washington points to unusually-high record temperatures, significantly increasing the risk for heat-related illnesses, especially for those outdoors, older people and residents without air conditioning. Even with a surge in recent years, The Seattle Times found the greater Seattle area continues to be the least air-conditioned metro in the United States, with just 44.3 percent of homes equipped with central air or wall units.

This heat wave is shaping up to be historic

A few factors can affect where the mercury ultimately lands each day, but forecasters have high confidence in a "long-duration, record-breaking heat wave," with risks of heat-related impacts ranging from "high" to "very high." The National Weather Service said breaking records in the coming days is certain — the only unknown is just how many may fall.

"Today marks the beginning of the heat wave that will really impact Western Washington over the weekend and into Monday," wrote Justin Pullin, senior meteorologist at NWS Seattle. "At first we will break the daily records, and then the June records, and then we will very likely break some all time record high temps."

HEATRISK ANIMATION Here's the latest look at the HeatRisk Friday through Tuesday. You can check out your local HeatRisk forecast here: https://t.co/UGH89gfYYw Bottom line: a record-breaking heat wave will occur this weekend into early next week across the PNW. #wawx pic.twitter.com/qNzd4oFcKr
— NWS Seattle (@NWSSeattle) June 25, 2021

Here is what forecasters expect for Saturday, Sunday and Monday:

Saturday

Saturday will see temperatures in the 90s for many across Puget Sound, with a few places on the Eastside and South Sound likely to crack triple digits early. The National Weather Service's HeatRisk map shows most of the region in red, the second-highest risk classification. Areas shaded red are classified as having "high risk for much of the population, especially those who are heat sensitive and those without effective cooling and/or adequate hydration."

A few notable highs in Saturday's forecast:

• Olympia: 100°
• Kent: 100°
• Redmond: 100°
• Puyallup: 99°
• Kirkland: 98°

Sunday

More cities are likely to cross into the 100s by Sunday afternoon, including the Seattle metro. Heat risks will begin to hit the magenta "very high" warning level, the highest of four classifications, in more areas, especially those furthest away from the water. Areas in magenta are classified as having "very high risk for entire population due to long duration heat, with little to no relief overnight."

A few notable highs in Sunday's forecast:

• Issaquah: 108°
• Bonney Lake: 105°
• Gig Harbor: 104°
• Bellevue: 103°
• Seattle: 102°

Monday

Forecasters expect Monday will be the hottest day of the heat wave, and it could become the hottest day on record in Seattle and other parts of Western Washington. Very high heat risks will extend further across Puget Sound, and the Seattle area could see afternoon temperatures as high as 112 degrees. By contrast, the coast will see a cool-off of about 10 to 15 degrees, forecasters said.

A few notable highs in Monday's forecast:

• Issaquah: 112°
• Sammamish: 110°
• Puyallup: 109°
• Seattle: 105°
• Tacoma: 100°

Is there any relief on the horizon?

After Monday's peak, forecasters expect temperatures to begin tapering off, dropping into the low 90s or upper 80s by Tuesday and moderating a little more Wednesday and Thursday. However, long-range forecasts still show temperatures well above normal for this time of year, and current modeling suggests Seattle may not see an afternoon below 80 degrees until after July 4. At this point, there is no rain and few clouds as far as the forecast can see.

How to spot heat exhaustion or heatstroke (from the Seattle Fire Department):

Signs of heat exhaustion include:

• Sweating
• Pale, ashen or moist skin
• Muscle cramps (especially for those working or exercising outdoors in high temperatures)
• Fatigue, weakness or exhaustion
• Headache, dizziness or fainting
• Nausea or vomiting
• Rapid heart rate

Heatstrokes are more serious conditions and can occur when the body's temperature reaches 104 degrees or higher. They often result from prolonged exposure to high temperatures or after physical exertion.

Added signs of heatstroke include:

• Confusion
• Altered speech
• Nausea or vomiting
• Rapid breathing and a racing heartbeat, among other symptoms.

Anyone exhibiting any of the four symptoms requires emergency medical attention, firefighters said.