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When will the prolonged heat wave end across the northwestern US?

By Brett Rathbun, AccuWeather meteorologist
July 28, 2018, 11:39:47 PM EDT

Hot weather will hold its grip across the northwestern United States through at least the end of July.

An area of high pressure sitting over the Desert Southwest will continue to pump heat northward over the next several days, according to AccuWeather Meteorologist Ryan Adamson.

Highs through early week will average 10 degrees Fahrenheit above normal. This will result in afternoon temperatures for most communities in the 90s and 100s F.

Seattle, which had four straight days of highs at or above 90 F spanning last Monday through Thursday, will flirt with 90 F again on Sunday and Monday. Normal highs in Seattle during the end of July are around 77 F.

NW Heat July 28

Portland, Oregon, reached at least 94 F for five straight days spanning last Sunday through Thursday.

The heat will fall short of records in most areas. Record highs in Seattle for the end of July range from the mid-90s to lower 100s F. Record highs in Portland through the end of July range from 99 to 107 F.

Anyone needing to spend time outside during the hottest times of the day are urged to drink plenty of water and wear light-colored clothing. Do not keep children or pets in your vehicle without running air conditioning.

"The prolonged heat will create stress for those in poor health or without air conditioning," Adamson said.

Those wanting a break from the heat are urged to visit the coastal beaches, where the air will be much cooler.

The lack of high humidity across the region has allowed the air to cool significantly overnight, with temperatures falling between 30 and 40 degrees Fahrenheit from the daytime highs.

This pattern will keep any precipitation chances away from the area. Seattle will likely end July receiving only 0.05 of an inch of rain, with 80 percent of that falling on July 1. Seattle typically receives 0.70 of an inch of rain for the entire month.

Portland has received only 0.02 of an inch of rain this month, with all of that precipitation falling on July 2.

Most rainfall through Sunday will occur over parts of Montana and Wyoming.

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This continuous dry weather pattern will do nothing more than worsen the drought plaguing the region. As of July 26, 2018, nearly 97 percent of the state of Washington is enduring abnormally dry to drought conditions, according to the United States Drought Monitor.

Almost 95 percent of Oregon is currently battling abnormally dry to drought conditions, with 55 percent of the state in a severe drought. Area reservoir water levels will continue to fall as a result.

This dry weather will increase the fire threat across the region. Prevent the ignition of new wildfires by properly disposing cigarette butts, and do not park your hot car on dry vegetation.

The stagnant air, combined with wildfires brewing across the area, will lead to poor air quality.

Those hoping for some relief may receive some during the first days of August.

NW heat relief July 28 pm

By Wednesday, temperatures in Seattle and Portland will drop closer to normal. This relief will still not come with any measurable precipitation.

It will take until Thursday for more noticeable relief to come to the interior communities of Spokane, Washington, and Pendleton, Oregon.

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