A high-pressure system hovering over Southern California is set to sizzle the region over the next week or so, forecasters said Tuesday as state officials issued a rare Flex Alert urging residents to conserve energy.
Temperatures in the Inland Empire, and elsewhere across the region, are expected to soar up to 10 degrees above normal, said National Weather Service Los Angeles meteorologist Joe Sirard. “Normal” temperatures for each day, he said, are calculated from daily averages collected locally over the past 30 years.
The coming spike in heat comes during a Southern California summer that has already had a series of heat spells.
The looming heat prompted California’s Independent System Operator, or ISO, on Tuesday afternoon to issue a Flex Alert calling for Southern Californians to reduce energy consumption from 4 to 9 p.m. Wednesday. The ISO, which oversees the state’s electric power grid, aims to ensure the reliability of the grid as power use is expected to go up amid abnormally high temperatures.
Sirard attributed the abnormal highs to an atmospheric phenomenon called upper-level ridging, which concentrates warm air over a particular place. This high-pressure system has been responsible for the consistent highs this summer.
“It’s a persistently warm pattern, especially in the inland areas throughout the week,” Sirard said. “There’s a persistent area of upper-level high pressure over the area. What that does is keep the hot weather over the region and away from the beaches.”
Sirard said areas with shallow marine layers like Woodland Hills and Van Nuys can expect the hottest temperatures. NWS forecasts daytime highs up to 102 degrees on Wednesday and into the upper 90s to finish the week. The San Gabriel Valley can also expect upper 90s averages into Thursday and Friday.
Downtown Los Angeles and Long Beach can expect averages in the upper 80s through Friday. Coastal communities can expect some reprieve with averages this week in the upper 60s to lower 70s.
Temperatures are expected to simmer down this weekend due to stronger onshore flow off the ocean, but the sizzle still isn’t likely to stop then.
“It’s the hottest time of the year. We’re cooling off probably closer to normal this weekend, but even in the valleys it’s still the upper 80s and lower 90s,” Sirard said. “Then it looks like the pattern might turn a bit warmer next week again, so probably another spell of five to 10 degrees above normal temperatures at some point next week.”
NWS San Diego meteorologist Stephanie Sullivan said that temperatures across the Inland Empire will reach the high 90s up to 104 degrees; San Bernardino and Hemet can expect highs of around 101, Lake Elsinore around 102. Inland Orange County will hit averages in the high 80s this week.
Given the persistent heat, this time of year in Southern California is ripe with wildfire potential. However, Sullivan noted that a recent spate of thunder and lightning storms could put the San Bernardino and San Jacinto mountains, where most of the fire rescue activity is concentrated, at particular risk.
These thunder and lightning storms, which Sullivan said usually occur over the mountain ranges every afternoon, are a result of a monsoon pattern that kicked off in July and is expected to persist into September.
Sullivan urged caution when driving, hiking, camping, or otherwise spending time in proximity to these storm hot spots.
“Any time thunderstorms are in the forecast, it’s better to go early in the day and try to get out of the area by noon or so because that’s when it tends to go off,” Sullivan added.
Along with being aware of possible thunderstorms, Southern Californians also should avoid strenuous physical activity in the heat, keep hydrated and remember to not leave animals or children unattended in cars.
The hottest parts of the day are early to mid-afternoon, so outdoor activities should be planned accordingly, she added.
“You definitely need to be weather aware,” Sullivan said.
Forecasted temperatures for Wednesday:
— Downtown Los Angeles: 88
— Fullerton: 91
— Long Beach: 83
— Anaheim: 92
— Mission Viejo: 91
— Pomona: 96
— Redlands: 100
— Riverside: 101
— San Bernardino: 101
— Lake Elsinore: 102
— Torrance: 81
— Van Nuys: 97
— Whittier: 93
Source: National Weather Service