The summer monsoon will debut this weekend, bringing moist, humid air to East County — and possibly producing lightning capable of starting wildfires in a region nearing the end of a two-week heat wave, the National Weather Service said.
The seasonal phenomenon is caused by high-pressure systems that transport lots of unstable air into the county from the Gulf of California and the eastern Pacific Ocean.
The monsoon often does little more than make the air uncomfortably humid. But lightning is always possible, especially in the mountains.
The monsoon will start weakly Friday but strengthen into the weekend, when temperatures east of Interstate 15 will still be in the upper 80s and low 90s. The deserts will range from roughly 110 to 115 over the next few days. Coastal areas will start to slowly cool Friday, largely because an onshore flow will deepen the marine layer.
Forecasters say the surf will be in the 1-to-3-foot range Friday and will produce comparatively weak rip currents from Oceanside to Imperial Beach. Sea surface temperatures will be 70 to 72 degrees.
Lifeguards advise swimmers and surfers to shuffle their feet when entering the ocean to scare off stingrays, which love to congregate in the warm, near-shore shallows.
