Seattle heatwave forecast: Models hint at 90s in Western WA

A possible Seattle heatwave is showing up on the long-range forecast, and Western Washington should pay attention. Take it with an appropriate grain of salt. Some forecast models are flirting with a real heat wave across the Puget Sound region in about 10 days. It’s not a lock. It could fall apart. But the signal is loud enough that a veteran Pacific Northwest meteorologist is telling people to pay attention.

KIRO Newsradio meteorologist Ted Buehner, who spent decades at the National Weather Service in Seattle, joined “Seattle’s Morning News” and walked us through what the latest weather model runs are showing. His message was measured. It was also clear. If this Western Washington heatwave pans out, it could be a problem.

“Right now, it looks like if these particular models match up, we may have another heat wave of some kind,” Buehner said. “We’ll probably get up into the 90s.”

Ninety degrees in Seattle is not a small thing. Most of us don’t have central AC. Our bodies aren’t acclimated to it. And the last time the atmosphere set up like this in late June, the 2021 Pacific Northwest heat dome killed hundreds of people across the region.

What the ECMWF temperature anomaly charts actually show

The maps making the rounds online come from the European model (ECMWF) forecast, and they show something called 850 millibar temperature anomalies. Sounds like jargon. It’s not that complicated.

Picture the atmosphere about a mile up. That’s the 850 millibar level. Meteorologists like to look at it because it’s above the morning marine layer and the low clouds, so it gives you a cleaner read on what kind of air mass is sitting over the region. The anomaly part is just how far above or below normal that air is for this time of year.

Right now, the ECMWF model runs for June 15-17 are showing that air a mile up over Puget Sound is running 14-16 degrees Celsius above normal. In Fahrenheit, that’s 25-29 degrees warmer than it should be up there. And when the air a mile up is cooking, the surface usually goes along for the ride. That generally means Seattle temperatures well into the 90s at street level.

How this Seattle forecast compares to the 2021 heat dome

So how does this stack up against the 2021 Pacific Northwest heat dome? Surface temperatures during that stretch ran 16 to 20 degrees Celsius above normal at the peak, according to the World Weather Attribution report on the event. Seattle hit 108 degrees on June 28, 2021. That was more than 30 degrees Fahrenheit above the normal high for late June. The upper-level ridge that drove it was later measured as a 4- to 4.5-standard-deviation event, which is science-speak for “this isn’t supposed to happen for another thousand to ten thousand years.”

Quick translation on “upper-level ridge.” Think of the atmosphere as a river of air flowing west to east across the country. Normally, that river has dips and rises in it. A ridge is a big rise, a dome of high pressure parked way up high, around 18,000 feet. When one of these ridges plants itself over a region and refuses to budge, it acts like a lid. Air sinks underneath it. Sinking air warms up. Clouds can’t form. The sun cranks for days. That’s the engine behind every major Pacific Northwest heatwave.

In 2021, the ridge that formed over British Columbia was the strongest ever measured in our part of the world. The current model runs show a ridge. They don’t show that ridge.

The 2026 model runs are hot. The anomaly numbers are actually in similar territory to 2021 at the mid-levels of the atmosphere. What’s missing, at least so far, is the historic upper-level ridge that made the heat dome the killer it was. That’s a real difference. It’s also why Buehner is watching the models instead of issuing a warning.

Why KIRO meteorologist Ted Buehner is paying attention

Buehner has been forecasting Pacific Northwest weather since the 1970s. He’s not a guy who cries wolf. So when he says this one is worth watching, that’s the signal.

He also has personal scar tissue from the last big one.

“I certainly remember because I was umpiring a game on Saturday, the first day of that heat streak, and I suffered heat exhaustion,” Buehner said. “So that’s one of the hazards with big heat waves like this.”

Don’t count on the Washington coast to bail you out

The usual move during a Seattle heatwave is to load up the car and head for Ocean Shores or Westport. Buehner said to check the forecast before you pack.

“You get what’s called offshore flow,” he said. “The air flow is moving from Eastern Washington and British Columbia out towards the ocean. It’s not uncommon for the coast to be even warmer than we are.”

During the 2021 heat dome, Quillayute on the Pacific Ocean hit 110 degrees. Forks beat Atlanta and Chicago. When the wind clocks around to the east, the marine layer gets shoved offshore, and the beach starts to feel like the Tri-Cities.

When Seattle forecasters will know more about the heatwave

Buehner expects the picture to firm up over the next four or five days.

“This is a case where you want to stay tuned,” he said.

That’s the honest answer. The models might lock in. They might fall apart. Both are still on the table.

How to prepare for a Western Washington heatwave

The honest answer on prep is to do the boring stuff now, while the forecast is still soft. It’s easier to walk things back than to scramble when the National Weather Service goes red.

Start with the house. Dig the window AC unit out of the closet and make sure it actually works before you need it. Check the screens. Find the box fans. If you don’t have AC at all, identify the nearest cooling center now and write the address on the fridge. King County, Pierce County, and Snohomish County all stand up cooling centers during heat events, usually at libraries and community centers.

Hydration matters more than people think. Water before you’re thirsty, not after. Cut back on alcohol and heavy caffeine during the worst of it. Both work against you in the heat.

Watch the people who can’t watch themselves. Elderly neighbors, kids, anyone on medications that mess with temperature regulation, and anyone who lives alone. A two-minute knock on the door during a heatwave has saved lives in this region. Many of the deaths in 2021 were among older adults who lived by themselves in apartments without AC.

Don’t forget the animals. Dogs and cats need shade and fresh water. Pavement gets hot enough to burn paws. Move the dog walk to early morning or after sunset. Livestock and backyard chickens need extra water and shade too.

Know the warning signs of heat exhaustion and heat stroke. Heat exhaustion looks like heavy sweating, weakness, nausea, and a fast, but weak pulse. Get the person cool, and get fluids in them. Heat stroke is the emergency version. Hot dry skin, confusion, a body temperature over 103, possible loss of consciousness. That’s a 911 call. Don’t wait.

Plan the weekend around the heat, not in spite of it. Move the long hike, the yard work, and the heavy outdoor projects to the front end of next week before the ridge builds in. The back end is when people get hurt.

The atmosphere will tell us more in a few days. Smart move is to be ready before it does.

Seattle heatwave FAQ

When could the Seattle heatwave hit? Current model runs target June 15 through 17 for the highest anomaly readings over Western Washington.

How hot could it get in Seattle? Buehner says if the models verify, Seattle could see highs in the 90s. The forecast is not locked in.

Is this another 2021-style heat dome? Not yet. The mid-level temperature anomalies are in similar territory, but the historic upper-level ridge that drove the 2021 heat dome is not showing up in the current model runs.

Will the Washington coast be cooler? Not necessarily. Offshore flow can push the marine layer out to sea, and coastal towns like Ocean Shores and Forks can end up hotter than Seattle.

Charlie Harger is the host of “Seattle’s Morning News” on KIRO Newsradio. You can read more of his stories and commentaries here. Follow Charlie on X and email him here. 

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