L.A.’s muggy misery: Intense humidity makes summer heat even more unbearable
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- Los Angeles is enduring an unusually muggy summer.
- Heat and humidity, with warm nights offering little relief, have prompted officials to warn of elevated risks of heat illness.
It’s not your imagination: This summer has been unusually sticky in Los Angeles, with humidity levels making conditions feel more like the Deep South than Southern California.
As summer heat settles over the Southwest, it changes the circulation in the atmosphere enough to pull up monsoonal moisture from the Pacific and Gulf of California, fueling warm rain and thunderstorms — or, in this case, mugginess.
The phenomenon is known as the North American monsoon, said Bryan Lewis, a National Weather Service meteorologist in Oxnard. This particular stretch of monsoonal activity has been notable for the L.A. area because it’s been prolonged, yet it hasn’t fueled any rainstorms that could offer relief from the heat, he said.
The remnants of Tropical Storm Elida, followed by Hurricane Fausto, have also pushed tropical moisture into the area, he said.
Exacerbating the conditions, the ocean water just off the coast has been unusually warm, with readings of 74 degrees off Hermosa Beach and 70 degrees off Zuma Beach as of Sunday, Lewis said.
The sea surface temperature at Scripps Pier in La Jolla was measured to be 75.7 degrees Monday afternoon. Normally, it would be around 68 degrees this time of year, according to Daniel Cayan, climate researcher at Scripps Institution of Oceanography at UC San Diego.
Cayan attributed the unusual warmth to a weather pattern that’s established itself over the past three months or so. Plentiful sunshine has heated the surface water, while winds have been too light to mix with the cooler water below, he said.
“We’ve got this warm lens of water not only along the Southern California coast but extending well down off of Baja, Mexico, as well,” he said.
That means the afternoon sea breeze that typically helps cool down conditions, especially in coastal areas, is warmer. “It’s still cooling things down but not to the degree that we expect — and that our bodies expect,” Lewis said.
The protracted heat and humidity, with warm nights offering little relief, has had weather and public health authorities warning of an elevated risk of heat illness on and off for weeks. Los Angeles County has seen an increase in emergency visits for heat-related illness during the heat wave, according to a heat-related illness and mortality dashboard maintained by the county health department.
Conditions should cool slightly Tuesday through Thursday, with drier air sweeping in from the northwest to offer even more relief, according to the weather service, which does not expect to extend a heat advisory that expires at 8 p.m. Monday for many areas. Humidity levels will remain a bit above normal, especially for coastal areas, due to the warm ocean temperatures, Lewis said.
Still, the heat is expected to again increase Friday through Sunday, prompting more advisories later this week, Lewis said. The moisture will also likely return, with conditions feeling similar to the past three weeks or so, he said.
By Saturday, temperatures will be 10 to 15 degrees above normal, according to the weather service. Forecasters expect the valleys to reach 100 to 110 degrees, the lower mountain and far interior areas to reach 105 to 112 degrees and the beaches to be in the 80s. More heat advisories will almost certainly be in place.
Although it’s unclear to what extent climate change is influencing this particular heat wave, scientists have found that global warming from the burning of fossil fuels is making Western heat waves more frequent, persistent, humid and lethal.
Forecasters also continue to warn of dangerous rip currents and elevated surf of 3 to 6 feet across Los Angeles and Ventura County beaches. A beach hazard statement is in effect through Wednesday afternoon.
Los Angeles County lifeguards reported performing nearly 2,000 ocean rescues over the weekend as millions of visitors flocked to the coast for a reprieve from the heat.
Hurricane Genevieve, which is whipping up the Pacific Ocean about 500 miles off the southern tip of Baja California, will also send big waves rolling toward beaches in San Diego County this week, creating hazardous swimming conditions, according to the National Weather Service.
Times staff writer Ian James contributed to this report.
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