Monsoons in Southern California? Here's why it's so cloudy

Maybe you've heard this phrase recently: monsoonal moisture.

We're experiencing it right now, and it brings rain to normally bone-dry Southern California in the summertime. 

"I think a lot of people are always intrigued to find out there is, in fact, a monsoon in the desert Southwest,"said Daniel Swain, a climate scientist at UCLA and author of the California weather blog Weather West. 

The National Weather Service (NWS) for Los Angeles tweeted out a warning about monsoon weather on Sunday. 

https://twitter.com/NWSLosAngeles/status/889254633876713472

Swain says this summer's monsoonal weather is coming a bit later than normal. But this week, the unusual weather pattern is expected to bring high heat and muggy conditions throughout the region.

It’s caused when normal wind patterns reverse and bring moist, warm air hundreds of miles from the south.

You might think winds from the south would be drier. 

"But actually, the source for that moisture - rather than being the Pacific Ocean — is the Gulf of California," Swain said.  "And that water is like bathtub warm.”

Besides more sweating, Swain says the monsoonal moisture can also bring dry lightning strikes — a big fire risk.

"If you get hundreds of lightning strikes, that’s hundreds of potential new fires," he said. 

The monsoon has already made things wetter. NWS reports that downtown LA set a rainfall record today — with no rainfall received for this date in 140 years. 

https://twitter.com/NWSLosAngeles/status/889571030045511681

Swain says the monsoon weather could also bring extreme heat to areas that don't normally see it. 

"It'll be interesting to see if that heat ends up making it closer to the coast over the next couple of the weeks as we get this increase in humidity and monsoon moisture," he said. 

Episodes of monsoonal conditions typically persist for a couple of days and historically occur between the months of July and September. Swain says we could see the weather pattern repeat a few times before the end of the summer.