The Worst Is Yet To Come For California's Central Valley Heatwave

An intense heatwave gripping California's Central Valley will continue through the end of the week. Forecasters expect high temperatures to crack 100°F across the region through Thursday before things tick closer to normal this weekend. 

Monday began the sweltering four-day slog as temperatures climbed into the 100s through California's Central Valley. Sacramento, Merced, and Bakersfield all reported a reading of 100°F at 4:00 PM on Tuesday, with temperatures in the 90s creeping as far west as San Francisco Bay.

The heat will keep on going through the end of the week. Here are the week's forecast high temperatures from the National Weather Service as of Tuesday afternoon.

Wednesday, May 27th:

Thursday, May 28th:

Friday, May 29th:

Temperatures will return to a more reasonable state by this weekend as the upper-level ridge responsible for the heat begins to weaken and move off to the east.

This week's heat wave is the result of a strong upper-level ridge that's parked over the western United States. The ridge intensified when it got pinched between two upper-level lows, one over Texas and the other over the eastern Pacific Ocean. The intensity of the upper-level ridge is the primary driver of the unusually intense heat. High pressure aloft fosters sinking air, which heats up as it descends toward the surface. The intense subsidence leads to crystal clear skies and an intense sunshine that roasts communities stuck under the pattern.

Some daily and monthly record highs are in danger of falling during this heatwave. There's a chance that Fresno will break its monthly high temperature record of 107°F on Wednesday. Sacramento will likely break a few daily records before the heat abates, and the capital could come close to tying its monthly record high of 105°F.

The geography of the Central Valley and the relatively dry air that dominates the region allows this part of California to get pretty toasty during the warm months. The average first triple-digit reading occurs on June 11 in Sacramento, June 2 in Fresno, and May 30 in Bakersfield.

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