Storms to help firefighters but spark new dangers in western US
Cooler air and storms moving into the western US will aid firefighting in some areas but also bring hazards, including flooding on burn scars and gusty winds that could ignite new blazes.
An approaching area of low pressure will bring a welcome change in conditions to the western U.S.
When cooler air and moisture move into active wildfire zones, they often benefit firefighting efforts. However, the developing pattern across much of the western United States this week may create challenges for firefighting and hazards in recently burned areas, according to AccuWeather meteorologists.
A significant cooling trend is underway for most areas west of the Rockies this week as a large southward dip in the jet stream moves in from the Pacific and intensifies over the region. This is good news for those wanting relief from the relentless summer heat.
Across much of the Pacific Coast states and Nevada, temperatures will settle 10–20 degrees below the historical average. For example, at Lake Tahoe, California, the mid-September high is typically in the mid-70s, but highs for Thursday are projected to be in the middle to upper 50s.
Farther south, temperatures in Las Vegas will be near 90 Thursday and Friday, compared to the historical average in the upper 90s. Around Los Angeles, highs will be within a few degrees of 80 for much of this week, where the average high is in the mid-80s.
Farther east, temperatures will also dip by 5-10 degrees compared to highs at the start of the week. In Salt Lake City, after highs near 90 into Wednesday, temperatures Friday and Saturday may be no higher than 80.
Unlike midsummer patterns, this setup is accompanied by significant moisture. While weather conditions will vary across the region, the moisture will lead to an uptick in showers, with repeated rounds in some locations.
Where rainfall occurs, it will help dampen fuels and aid firefighting efforts.
Pockets of soaking rain will come and go during the week in parts of Nevada, Idaho, western Montana, Utah, Central California, Wyoming and Colorado.
With this event, rain will tend to avoid California's Central Valley, as well as the vast majority of Southern California, Las Vegas and Phoenix. There can be some dry, gusty storms over the deserts, which can kick up dust with little notice.
Rainfall may also bring new risks to burn scar areas
"Some of the rain can pour down at a heavy rate and lead to mudslides and flash flooding in recent burn scar locations," Buckingham said.
In this case, there is little to hold back the soil and ash, which can be quickly transported downhill during downpours in small streams and ravines in the steep terrain.
Moisture-rich storm will bring additional hazards
"Strong winds are expected to sweep across the Great Basin and in the southern and central portions of the Rockies from mid- to late week," Buckingham said. "Despite some beneficial rain over the past month, the gusty winds and dry conditions will elevate wildfire concerns."
Where thunderstorms occur with little or no rain in the pattern this week, lightning can spark new wildfires.
This pattern of lower-than-average temperatures and storms pressing into many Western states from the Pacific is expected to last through most of this week.
"During this weekend and next week, the jet stream dip will dissolve, temperatures will trend back to near the historical average, and the coverage of showers and thunderstorms will diminish substantially," Buckingham said.
As of Sept. 9, approximately 48,000 wildfires have burned 4.3 million acres for the year, according to the National Interagency Fire Center (NIFC). This is slightly below the 10-year average of 5.8 million acres for the same period.
The 6-5 Fire burned a structure on Tuesday, Sept. 2, 2025, in Chinese Camp, California. (AP Photo/Noah Berger)
Of the 15 active fires in California on Wednesday, the Garnet Fire was endangering the giant sequoias in the Sierra National Forest. The fire has consumed 56,000 acres and was only 15% contained.
While cooler air and moisture will aid fire control, smoke from ongoing fires will continue to create hazardous air quality. The moisture may trap some of the smoke near the ground where fires remain active.
Areas receiving substantial rainfall this week may have reduced fire risk for a couple of weeks, until the landscape dries out again.
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