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Rain, mountain snow to accompany push of cooler air across northwestern US into the weekend

Summer will take a brief hiatus across the northwestern United States as a storm system brings fall-like weather into early next week.

The jet stream will dive southward and allow for an unsettled and cooler weather pattern to set up and stick around for several days.

The jet stream is a narrow zone of strong winds in the upper levels of the atmosphere that guide storm systems and temperature patterns across the globe, with cooler air to the north and warmer air to the south.

Showers will spread inland across Washington, Oregon and Idaho through the workweek before spreading across the northern Rockies this weekend.

"Rumbles of thunder will be possible with some of these storms as well as small hail," AccuWeather Senior Meteorologist Matt Rinde said.

July is the driest month of the year across the Northwest with most locations averaging less than one inch of rain. However, enough rain could fall late this week to produce more than half of the entire month's average rainfall.

Cold air may allow snow showers to occur at elevations as low as 7,000 feet, which could impact travelers visiting national parks or mountain hikers. This includes the Washington and Oregon cascades, Bitterroots and Yellowstone National Park.

"Some minor accumulations will be possible, mainly over the highest mountain peaks during Saturday night," Rinde said.

The clouds and precipitation will also bring temperatures more typical of October to the area.

Highs will drop roughly 15 degrees below normal across parts of the Northwest.

Highs into next week will be in the 60s to near 70 on most days from Seattle to Portland, Oregon. Highs this time of year are generally in the mid- to upper 70s.

This cooler air will be a big contrast from the heat across the Eastern states.

The changing weather pattern, however, will be beneficial for firefighters battling wildfires.

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At least four wildfires are ongoing across portions of Idaho and Montana, according to the National Interagency Fire Center.

"Multiple days of wet weather will help crews contain current fires and limit the development of any new blazes," AccuWeather Meteorologist Renee Duff said. "Soil moisture that has been depleted by a recent dry stretch will be replenished, helping to invigorate any dry vegetation."

This storm will spread eastward across the North Central states by the middle of next week, allowing for sunshine and summerlike weather to return.