Southwest Bakes Under Summerlike Heat

A historic heat wave is underway in the West that will also spread into parts of the Plains smashing all-time record highs for March, perhaps even April, and this will have staying power in the Southwest into next week.

(MAP: Temperatures Right Now)

March Records Already Set

Eleven cities in California and Arizona have already tied or set new March record highs.

For the first time in 96 years, Redwood City, California, hit 90 degrees in March on Monday. They did it again Tuesday, topping out at 93 degrees.

Other March records have been set in Santa Ana, California (100 degrees Tuesday) and tied in Flagstaff, Arizona (73 degrees Tuesday).

Heat Wave Shifts To Higher Gear

There’s much more ahead in this heat wave.

The National Weather Service has issued extreme heat warnings and heat advisories in the Southwest. This is the first time a heat advisory has been issued in the Bay Area during in March.

(MORE: Heat Safety And Preparation)

It will not only intensify in the Southwest, but it will spread throughout much of the West into parts of the Plains later this week into the weekend.

While some cooler air will slide into the northern and central U.S. beginning Sunday, record heat will persist in the Southwest into at least the first half of next week.

How hot are we talking about? Think mid-summer heat as we’re turning the page officially to spring in mid-late March.

Triple-digit highs: The Desert Southwest, including Phoenix, Tucson, possibly as far north as Las Vegas, and parts of the L.A. Basin are forecast to see 100-degree-plus highs for multiple days. This weekend, a few of the hottest locations in the Southern Plains could also reach the century mark.

90s: California’s Central Valley, even parts of the Bay Area, will rise into the 90s for multiple days. This weekend, 90s are possible as far north as Nebraska, Colorado and Kansas. And that could reach as far east as Omaha and Kansas City.

(MAPS: 10-Day US Forecast Highs, Lows)

Historic Notables

Again, we’re not just talking about records set for a specific calendar day. This heat wave could set records for any March day in over 100 cities from California to Montana to Nebraska to Texas.

Prior to this, Phoenix, Arizona, had only hit 100 degrees once in March. They’re expected to see at least four, if not more, straight days of triple-digit highs in this heat wave. In an average year, they typically don’t reach 100 degrees until May 2.

Kansas City hasn’t reached 90 degrees in March since 1910. They might do that this weekend. In parts of the Plains, highs this weekend could be as much as 40 degrees warmer than average.

Perhaps most impressive is some all-time March records for entire states could be in jeopardy. According to weather historian Christopher Burt, 10 states from Arizona and California to Wyoming to Oklahoma could threaten their all-time state March records, including:

• California: 107 at Mecca on March 21, 2004

• Arizona: 104 at Yuma on March 21, 2004

• Colorado: 96 at Holly on March 19, 1907
• Oklahoma: 104 at Frederick on March 27, 1971

But wait, there’s even more. Burt also noted the U.S. all-time March record of 108 degrees in Rio Grande City, Texas, is also in jeopardy.

If that city sounds a little familiar, this Deep South Texas reporting station recorded what may be the nation’s hottest winter temperature just over a month ago.

Put simply, this may be most significant, long-lived March heat wave the nation has experienced since the March 2012 heat wave rewrote the record books in the central U.S. and Canada.

Why So Hot So Soon?

The reason for why this heatwave in particular has to do with the ridge of high pressure, also known as a heat dome, that is parked over the West.

This heat dome is record breaking for March, comparable in strength to ones we see in June. You can see the general position of the high pressure on the graphic below.

Record high pressure? Record temperatures. Temperatures we are seeing this week… in March... are comparable to what we should be seeing in summer.

This heat dome will eventually weaken and flatten a bit later next week.

Snow Drought, Climate Change

The warmest winter on record in much of the West has already left snowpack at its lowest levels in at least two decades from the Rockies of Colorado to the Oregon Cascades.

As the graph below shows, Colorado’s snowpack is least for any mid-March in the last 40 years, according to the USDA’s National Water and Climate Center.

After feet of snowfall in early February, California’s Sierra snowpack has since dwindled to only 42% of average for this time of year, according to the California Department of Water Resources. Melting snow in spring and summer typically supplies 30% of the state’s water. Fortunately, the state’s reservoirs are higher than average due to recent wet years.

This heat wave will further deplete the already paltry snowpack in the West. That could lead to an expansion of drought in the Southwest and higher fire danger early this summer before the summer monsoon kicks in, according to outlooks by NOAA and the National Interagency Fire Center.

And this heat wave appears to have climate change’s fingerprints on it.

According to an analysis by Climate Central, the magnitude of this heat wave by March standards has been made at least five times more likely by climate change.

Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him on Bluesky, X (formerly Twitter) and Facebook.