It’s really hot, Seattle. But cool winds — and maybe even rain — are just behind this heat dome

Yes, a heat dome is camped over us, and, yes, smoke could arrive as soon as tomorrow. And everything sounds terrible. But hold on, Seattle.

A cool west wind, a 20-degree temperature drop and maybe even rain are expected Sunday night if we can just hang on.

The high temperature in Seattle was expected to hit 90 degrees on Wednesday, which it had done by 4:30 p.m., and was expected to climb to the mid-90s on Thursday, Friday and Saturday.

But it’s not just the daytime highs that make this heatwave so dangerous for residents of the Pacific Northwest. Overnight lows, typically at 58, could reach 68 or 70 over the next four days, said National Weather Service meteorologist Matthew Cullen.

“That’s why we have the excessive heat warning out,” he said. “With extreme heat during the day and no relief at night, it can accumulate.”

Excessive heat throughout the United States has prompted the National Weather Service to place more than half of the Lower 48 states, including Western Washington, under warnings and alerts. Nearly 195 million Americans are under some sort of heat watch through the weekend, the weather service said.

Our current heat wave is due to a strong high pressure area that’s trapping warmth close to the surface of the earth like a lid or a dome, Cullen said. It’s not as strong as the one responsible for our record-smashing June highs, but still dangerous, he said.

Drink plenty of water and get to a cooling center if you don’t have air conditioning, he said. Spending even a couple hours a day inside a cooled library, community center or public cooling center can go a long way toward preventing heat stroke and heat exhaustion, Cullen said.

With this weather pattern, Cullen said there’s a possibility we’ll see the development of a northeasterly wind on Wednesday afternoon, potentially bringing smoke from fires in North Central Washington and British Columbia into the Puget Sound area Thursday morning.

Much of the smoke would likely be in the upper atmosphere, but some could be closer to the surface, he said.

By Sunday, he said, the heat dome will slip to the east and onshore winds will bring moisture and much cooler temperatures. Highs in the upper 70s, along with rain, are possible by Sunday night or Monday morning.