Southern California heat wave rolling in early next week

A prolonged heat wave is forecast to blanket the region starting Tuesday, May 20, pushing highs into the triple digits in some Southern California inland spots before retreating on Thursday.

But cooler temperatures and patchy drizzle are expected across Southern California this weekend, with a deep marine layer and the cool conditions lingering through Saturday, with highs in the 60s and light drizzle possible, according to the National Weather Service.

Beginning Sunday, a high-pressure ridge is forecast to build over the region, triggering a steady warming trend.

“Next week is going to be a hot one and lasting at least two days longer than the previous heat wave,” the NWS stated.

After highs reach the 70s on Sunday, a shallow marine layer could bring dense fog to coastal Los Angeles County on Monday morning, but it’s expected to clear quickly, forecasters said.

Temperatures across most areas are forecast to climb another 5 to 10 degrees by Monday afternoon. The western San Fernando Valley could near 90 degrees, up to 15 degrees warmer than Sunday.

Starting Tuesday, highs are expected to mirror the September-October heat waves, reaching the low 100s in the warmest valleys, the low 90s in downtown Los Angeles and the 80s in most other areas away from the coast, according to forecasters.

The conditions could warrant another round of heat advisories for the coastal valleys and possibly even parts of the interior coastal plain, according to the NWS.

Onshore flow is expected to return Thursday, bringing a gradual cooling trend heading into next weekend.

In the Inland Empire, Wednesday and Thursday are likely to be the warmest days, with daytime highs hitting the mid to upper 90s on both those days, forecasters say.

Referring to the chance of light rain this weekend, the NWS wrote on X, “As we move toward the end of May, chances for widespread precipitation dwindle to near zero through the summer months, making this possibly the last round of measurable rain for a while.”