A strong ridge of high pressure will build over the Western U.S. this weekend, resulting in record-challenging warmth from Arizona to California and northward into Idaho. 

Temperatures have already been quite warm this week, but they will begin to trend even higher on Friday with highs soaring well into the triple digits across the desert regions of Arizona, Nevada, and California. Check out our high-resolution Temperature Forecast Map for Friday afternoon.

It will be plenty hot on Friday, but the heatwave will be most intense on Saturday and Sunday when numerous record highs are likely to be broken across the West. 

Many areas in the Western U.S. are under either an Excessive Heat Warning (the most severe warning for heat) or a Heat Advisory (less severe heat) through the weekend of July 15th-16th per the National Weather Service.

Here is the National Weather Service Watches/Warnings/Advisories Map as of Thursday afternoon (July 14).

The heatwave is expected to peak this weekend, but only minor relief is expected heading into next week. High pressure will continue to dominate the weather pattern across the Southwest and West Central U.S. with temperatures running above average for the foreseeable future.

After a cooler-than-average June for much of the West, summer heat has come on strong during July with a quick transition to above-average temperatures. 

Southwest U.S.

In terms of anomalous warmth, the western part of the Southwest will be most heavily impacted by this heatwave, including Utah, Arizona, and Nevada. 

Check out our 10-day forecasts for Salt Lake City, St. George, and Las Vegas with average and record temperatures also listed for perspective.

Salt Lake City
Average High: 95ºF
Record Highs: 103º-107ºF over the next 7 days

St. George
Average High: 102ºF
Record Highs: 112º-115ºF over next 7 days

Las Vegas
Average High: 105ºF
Record Highs: 114-117ºF over the next 7 days

Higher elevation areas will be cooler of course, but even more temperature locations such as Flagstaff will be flirting with record highs.

Flagstaff
Average High: 82ºF
Record Highs: 92º-94ºF over the next 7 days

California

The Golden State made it through June with below-average temperatures and a lack of heatwaves. However, this upcoming heatwave will be brutal for desert and central valley locations, where highs are expected to reach well into the triple digits for some areas.

Heading up into the Sierra Nevada Range will feature more tolerable temperatures, but it will still be quite hot around Tahoe with highs reaching the 90s in Truckee.

Truckee
Average High: 82ºF
Record Highs: 95-98ºF over the next 7 days

The higher you go in the Sierra this weekend, the better. Temperatures at Mammoth Lakes will be approaching record levels, but it will still be much cooler there compared to most areas.

Mammoth Lakes
Average High: 78ºF
Record Highs: 85º-87ºF over the next 7 days

Idaho and the Interior Northwest

The heat will extend northward into Idaho, as well as central and eastern portions of Oregon and Washington where highs in the 90s to 100s can be expected across valley and lowland locations. 

Boise and portions of the Snake River Plain in Idaho will see the worst of the heat across the Interior Northwest.

Boise
Average High: 94ºF
Record Highs: 105º-111ºF over the next 7 days

Even Sun Valley will feel the heat this weekend with highs rising into the 90s in Ketchum and across the Wood River Valley.

Ketchum
Average High: 81ºF
Record Highs: 92º-98ºF over the next 7 days

If you have outdoor plans across the West this weekend, be sure to head out early in the morning when its coolest and bring plenty of water. High-elevation areas, coastal areas, and lakes will be your friend this weekend.

And as always, be sure to use our Forecast Anywhere feature to get pinpoint daily and hourly temperature forecasts for any location and elevation.

Alan Smith