Fox News Weather Center

Oppressive heat to envelop the western US as weekend highs soar 10 to 15 degrees Fahrenheit above average

Highs will run between 10 and 15 degrees Fahrenheit above average across much of the western United States into the upcoming weekend.

"As a strong area of high pressure builds over the Great Basin, some cities in the West will experience their first prolonged heat since early June," AccuWeather Meteorologist Ryan Adamson said.

Some cities across the Pacific Northwest will have at least three consecutive days or more of 90-degree heat which will classify this stretch of weather an official heat wave.

"Cities such as Medford, Oregon and Boise, Idaho, will have highs topping out near or slightly above 100 through Friday," Adamson said.

The warmer air will finally make a return to Portland, Oregon, as the city has yet to hit 90 since June 6.

"While temperatures in July have been more moderate in Portland thus far with no 90-degree highs yet, that will be changing during the end of the week," AccuWeather Meteorologist Dan Pydynowski said.

The 90-degree heat is not expected to stretch as far north as Seattle, where highs should top out in the middle 80s. Along with low humidity, the weather will be fantastic for any outdoor activities in the city.

The last time Seattle reached 90 was on June 5.

This warmup will not only be felt across the Northwestern states, but also across the Southwest.

California's Central Valley will be stuck in triple-digit heat into the weekend. Record highs will be challenged in Sacramento, Redding and Fresno.

While humidity levels will remain low, the heat in some locations will still be enough to increase heat-related illnesses, such as heat exhaustion and heatstroke.

Those needing to be outside should wear light-colored clothing, take frequent breaks and drink plenty of water. Those needing to do shopping at a local mall or get groceries should plan to do so during the morning or evening hours.

Those looking to beat the heat may want to consider traveling to coastal beaches where the air will be cooler and more comfortable.

Late July into early August is typically the peak of the heat across the Western states. Average temperatures after early August will head downward as the fall approaches.

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The heat will be bad news for firefighters battling wildfires across the West, especially the Sand and Soberanes fires in California.

Help prevent starting new wildfires by properly extinguishing any cigarettes and keep grill flames to an appropriate height to prevent flare-ups.

Monsoon thunderstorms will continue across portions of the Intermountain West, where any dry thunderstorm could spark another wildfire.

Winds will remain rather light across the West into the weekend, which will help in preventing the fire from spreading too quickly.

Some heat relief will be in store by the weekend.

"The high will weaken over the weekend, sending temperatures closer to normal," Adamson said.

Highs by the weekend will range from the 70s to lower 80s in Seattle and Portland to the 90s in Medford and Boise. Highs across much of the Central Valley will still be near or above 100.