Big heat coming to western US following Independence Day weekend

Yahoo

14 hours ago

Heat is poised to build over much of the western United States next week and may challenge the highest temperatures of the season so far, along with boosting an already volatile wildfire risk, AccuWeather meteorologists caution.
The heat will arise following typical summer conditions for much of the West for the Independence Day weekend.
"At its peak during the first full week of July, some places will be 15 degrees above average, and isolated spots could be as much as 20 degrees Fahrenheit above the historical average," AccuWeather Senior Meteorologist Heather Zehr said. "This could be an extended stretch of heat away from the Pacific coast."
July typically brings the highest temperatures of the year on average to the interior West, so when forecasts call for readings of 15-20 degrees above that level, it is significant, even for the middle of summer.
Once the heat wave begins to build and the strength of the weather setup is realized, high temperature adjustments to the forecast are likely. Temperatures could rival season-high marks set during late May and June.
The hottest it's been in Phoenix, Arizona, and Palm Springs, California, is 117, while Las Vegas has reached 110, with Salt Lake City hitting 104 and Fresno and Sacramento, California, touching 102.
"A large area of high pressure will start to build over northwestern Mexico and the interior Southwest through this weekend," Zehr explained. "The high pressure area will cut off tropical moisture that has been bringing rounds of drenching thunderstorms and dust storms recently to the interior West. As the high strengthens early next week, it will also expand to the north and west, reaching interior portions of the Northwest as well as California."
The heat wave is not likely to eclipse season highs along the immediate coast of California. Downtown Los Angeles reached 99 on May 10. San Francisco peaked at 81 in early May. However, as Zehr pointed out, some heat will surge into the Northwest, and temperatures will climb in coastal areas of Washington and northern Oregon next week where highs of 96 in Portland, Oregon, and 90 in Seattle, so far this season, could be challenged.Have the app? Unlock AccuWeather Alerts™ with Premium+
Wildfires already causing trouble in the West
Existing drought conditions and dry vegetation have already been contributing factors to an active wildfire season.
One of the most recent fires broke out in the mountains of San Luis Obispo County, California. In a matter of hours, the Madre Fire grew rapidly in size to 35,000 acres as of Thursday morning and has already become the state's largest wildfire of 2025 so far.
In prior decades, wildfires occurred predominantly during the late summer and autumn seasons. However, with vast areas of drought and episodes of strong winds becoming more routine, wildfires are becoming a year-round problem in the West.
Wildfires have been especially troublesome over the southern Canadian Prairies this spring and summer. Northwest breezes have occasionally sent a considerable amount of smoke from those fires into the central and eastern United States.
People are urged to exercise extreme caution with campfires, fireworks and power equipment.
"The building heat into next week will further dry out the vegetation and raise the risk of wildfire ignition next week and beyond," Zehr said. "We are not seeing any mechanism to bring widespread rainfall to areas from the Great Basin to the Pacific coast, which is not surprising."
The North American monsoon became active in recent days, and that was the main cause of the surge in showers and thunderstorms over the interior Southwest this week. However, with drier air working in and shunting the plume of moisture off to the east, downpours will be limited at best over the southern Rockies next week.
A small amount of moisture left in the atmosphere could trigger spotty, but mainly dry, thunderstorm activity over the interior Southwest this weekend to next week. Dry thunderstorms still produce lightning strikes, which could spark new wildfires.
Fortunately, light winds appear to be in store, which should limit the risk of rapidly spreading fires, except for freak local conditions.
Taking extended, ill-advised hikes over the interior West can be hazardous. In addition to the ever-present risk of snakes and other wildlife, the midsummer sun and heat can be highly unforgiving. And, on a number of days during the mid- to late summer, afternoon thunderstorms can bring the risk of sudden lightning strikes and flash flooding over the rugged terrain.
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