Weather update: Seattle, Portland could see record heat 20-25 degrees above normal

 Record-breaking heat will bake Seattle and Portland again Sunday, and there is no relief in sight until the middle of the week, forecasters say.

Temperatures are far beyond normal for the spring, 20 to 25 degrees higher than usual for May, prompting the National Weather Service to issue heat advisories from the Canadian border south into California.

Meanwhile, in Texas parts of the state including the Houston area could get hit with bands of heavy rain, bringing the possibility of flash flooding.

Seattle, Portland brace for record temperatures

Portland, Oregon, and Seattle will sizzle on Sunday after an already sweltering Saturday.

"We could see another day of record temperatures Sunday. Portland could top the low to mid-90s," said National Weather Service meteorologist Zach Taylor at the Weather Prediction Center.

Seattle highs could top out in the upper 80s and perhaps 90 degrees, which would be a record as well, he said.

PACIFIC NORTHWEST IN THE OVEN:A record-breaking heat wave is forecast for the Pacific Northwest this weekend

"Normal temperatures in Seattle in May would average a high in the mid-60s, so we're looking at readings that are going to be 20 to 25 degrees above normal. That's pretty significant," he said.

High temperatures in the region are rare and few homes are built with them in mind. The Seattle area has one of the lowest rates of homes with access to air conditioning in the nation, at about 53% according to the 2021 American Housing Survey by the U.S. Census Bureau. With increasing heat waves hitting because of climate change, that figure has increased from 31% in 2013.

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The high temperatures could continue well into the coming week, but there is a possibility of cooling thunderstorms and showers in some areas Tuesday or Wednesday, said Jake Sojda, a meteorologist with AccuWeather at its State College, Pa.

Those could bring their own problems because some of those thunderstorms could be dry, bringing thunder and lightning strikes but no rain. "It's a double-edged sword," he said.

"You could have lightning strikes on vegetation that's drying out in the heat. Some of the storms could provide heat relief but also pose a wildfire threat," he said.

Low-lying parts of Houston at risk for flooding

A plume of moisture that's stretching from the Gulf of Mexico through Texas and into the Central Plains states is carrying heavy rains that are hitting Texas and especially the Houston area, Taylor said.

"They already had 1 to 2 inches of rain that fell locally overnight and early this morning. They've now got the potential for another 1 to 2 inches and maybe higher amounts locally," he said.

That could mean as much as 4 or 5 inches of rain in some parts of the greater Houston area over the course of Sunday.

"There's already been plenty of flash flooding reported in between San Antonio and Houston through the weekend. This will continue to push slowly eastward and start to dissipate over the course of the evening," Sojda said.

The heavy rain extends up across portions of central Oklahoma, across eastern Kansas and into northern Missouri.

While there is some danger of heavy rains and possible flooding as the storms travel north, in general, the threat has been minimal, Sojda said.

"That's been more of a steady rain and that's been beneficial because there's been a drought in some of those areas. The rain hasn't been so heavy that it's been damaging," he said.

Texas tornado cleanup continues

The southern tip of Texas is still cleaning up after a powerful tornado tore through the community of Laguna Heights at about 4 a.m. Saturday, killing one person and sending at least 10 others to local hospitals.

The tornado hit as most people were in their homes asleep in the unincorporated community of Laguna Heights, located on the mainland across from South Padre Island, off the Gulf of Mexico.

Unlike hurricanes, where advance warning is possible, there's no way of knowing when tornadoes will hit. The first warning of a tornado “went out at the same time it was touching ground,” said Barry Goldsmith, a warning coordination meteorologist for the National Weather Service in Brownsville.

Calm, mild week for the rest of the nation

Outside of the Pacific Northwest and flood watch areas, the rest of the country could be in for a pleasant week, Sojda said.

"It looks to be quiet and pretty nice across the northern tier for the next couple of days," he said. "Expect dry, sunny and mild."