Building High Pressure Ushering in Heat Wave Across Interior West

The first heat wave of the summer is bearing down on the western U.S., threatening parts of the region with readings in the triple digits. Here is a look at how toasty it is going to get and when to expect the mercury to start climbing.

Mercury Forecast to Soar Across Interior West by End of the Week

Just in time for the start of June, the West is predicted to bake as the first heat wave of the year bears down on the region. Highs will reach the century mark in some parts of the interior West before a wave of cooler air and rain showers work to trim the heat beginning this weekend.

A large area of high pressure is currently building over the interior portions of the West, ushering in the unseasonably warm weather. A general offshore flow sending the winds from the land and out to the water will also work to prevent cooler ocean air from reaching farther inland. The strong high-pressure system to the north and a storm that is brewing over the Pacific southwest are partnering to cause the offshore flow.

While Southern California experienced a heat wave earlier in May, this upcoming weather pattern will be the first major blast of sizzling temperatures for much of the region. Forecasters are warning that daily highs could be challenged in some communities in the days ahead.

The areas located closest to the coast will see the warmest readings on Friday. Conversely, the interior portions of the western U.S. will notch the top temperatures on Saturday. The Pacific Northwest will also get in on some of the heat to a lesser degree.

A bit of a sea breeze will help to mitigate the heat in coastal areas. However, you can still expect temperatures to reach about 5 to 10 degrees over the historical average before the breezes kick in. For instance, San Francisco is forecast to see readings reach the low 70s on Thursday and Friday. This compares to the historical average for the Bay Area of readings in the upper 60s.

As noted earlier, it will be much warmer moving inland. Sacramento is forecast to see a high of about 103 degrees on Friday under mostly sunny skies. The state capital of California will cool slightly on Saturday with highs in the upper 90s before falling into the mid 80s on Sunday.

Moving to the north, Redding is forecast to see 107 degrees on Friday before sliding a few degrees to 105 on Saturday. Sunday's readings will top out in the mid 90s before more significant relief arrives on Monday with highs of about 84 degrees.

Fresno, California, is likely to experience the peak of the heat wave on Saturday with a forecast high of about 106 degrees along with mostly sunny skies. Like the rest of inland California, residents will need to wait until Monday for noticeable relief from the heat.

Pushing deeper inland, Boise, Idaho, is expecting the crack the century mark on Saturday. Temperatures will remain in the low 90s on Thursday and Friday. Sunday will usher in dramatically cooler temperatures for Boise with a forecast high of 85 degrees.

Salt Lake City is forecast to hover in the 90s through the weekend. Although this is moderate compared to the heat gripping other parts of the region, it is important to keep in mind that the average readings for late May bounce around in the upper 70s in this part of Utah. The highest temperature recorded so far in Salt Lake City in 2025 was 89 degrees on both May 10 and 12.

Southern California will dodge the worst of the heat associated with this weather pattern. Los Angeles is forecast to see readings max out in the mid 80s on Friday and Saturday.

Not surprisingly, temperatures will continue to sizzle in the interior Southwest. Las Vegas could eclipse the century mark on Wednesday. It will get warmer from here with readings of about 106 degrees on tap for both Thursday and Friday. The top reading achieved in Sin City thus far this year happened on May 22 when the mercury hit 100 degrees.

Wildfire Risk Elevated

The building heat will also raise the risk of wildfires in the short term. Drought conditions are also expected to expand due to the dry weather pattern. California has not seen significant rainfall since the end of March. This has created widespread areas of parched vegetation susceptible to being used as fuel for wildfires.

The air circulating within the core of the heat will also be dry in nature. The onset of windier conditions will aid in the spread of any fires to erupt. Those headed out for outdoor activities in wooded areas this weekend will want to be particularly careful about the risk of wildfires.

When to Expect the Hot and Dry Pattern to Break

The core of the heat will begin to break up later in the weekend and into next week thanks to the arrival of two storm systems. The first weather maker will plunge to the southeast after getting started in the northern Pacific Ocean. This storm will initially impact the Northwest with rain showers.

The second system is part of a dry storm that is expected to come together off the coast of Southern California. Forecasters will be watching this system to see how much moisture it will be able to gather from the tropics and send to the north. The end result could be similar to the type of rain that typically falls as part of the North American monsoon season.

Additionally, meteorologists are monitoring an area in the eastern Pacific that could birth the first tropical rainstorm of the season. Hurricane experts have been warning for days that this system could become the first named tropical feature of the year by late Wednesday or Thursday.

Should this system come to life, it will go by the name of Alvin. The moisture produced by the feature could extend into the southwestern corner of the U.S. by late in the weekend.

Although the arrival of tropical moisture would be good news for increasing drought concerns, the lightning that typically accompanies tropical weather events could also raise the threat of wildfires in areas where little rain falls.

Regardless of the amount of precipitation that falls over the West, both of the storms will serve to trim the temperatures as the weekend comes to a close.

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