I was in the Bermuda Dunes area this past week, and the weather was pretty darn interesting. Unfortunately, I had meetings in the early part of the week when the weather was nice, and by Wednesday afternoon it was cloudy. By Wednesday evening, it was raining, and boy did it ever rain!
I kept getting flash flood warnings on my phone-- I've spent a lot of time around that area, and I wasn't worried. Flash floods are an issue in the washes and drainage basins, but if you stay out of there and the rain isn't worse than torrential, you'll be fine.
On Thursday morning, though, the washes were running pretty high. These are basically dry rivers most of the time-- so dry that they have roads running through them. Once a year or so, they fill up, and it's crazy to see. I had to drive down there and take a look.
Fortunately, I wasn't planning to head home until Friday morning, but I was watching the weather. I honestly don't think I would have gone on Thursday. The PIREPs were showing moderate-severe icing up into the lower flight levels, and moderate- severe turbulence in the upper 20s. Part of the issue was a 170-200 knot jetstream perched right over central California, running west to east. Not to mention moderate rain and severe turbulence over the Palm Springs area!
I left on Friday morning, and no issues-- a few bumps climbing out, and smooth pretty much all the way. I flew home at FL220 to stay below the turbulence (ATC said it was bad above FL230), and kept me just above the tops so no icing. An easy trip, really.