Aberrant March Heat Wave Hits Southern California to the Bay Area

West: How Many More Hot Days Until Relief Arrives?

A historic heat wave is underway in California smashing all-time record highs for March, perhaps even April, and this will have staying power in the Golden State into next week.

(MAP: Temperatures Right Now)

March Records Already Set

A number of cities in California have already tied or set new March record highs.

Redwood City, California, hit 90 degrees in March on Monday - the first time in 96 years, and this continued into Tuesday, topping out at 93 degrees.

Santa Ana, California also hit a March-record 100 degrees on Tuesday.

Heat Wave Shifts To Higher Gear

This heat wave is not going anywhere.

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

(MORE: Heat Safety And Preparation)

The heat will continue to intensify across the state, and will spread throughout much of the West.

What kind of heat? Think deep summer heat as we're changing seasons officially into spring in mid-late March.

Triple-digit highs: cities in the L.A. Basin are forecast to see 100-degree-plus highs for multiple days.

90s: from the Central Valley to parts of the Bay Area, temperatures will rise into the 90s for multiple days.

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

Historic Notables

Downtown Los Angeles has never hit 100 degrees in March. They have a low chance of doing that in this heat wave.

Some all-time March records for entire states could be broken. Per weather historian Christopher Burt, 10 states including California could threaten their all-time state March records: California: 107 at Mecca on March 21, 2004.

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.

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.