The first heat wave of the summer will hit the Southland Thursday, sending temperatures into triple-digit territory and creating an elevated danger of wildfire and heat-related illnesses amid high temperatures, strong winds, low humidity and an abundance of very dry vegetation, forecasters said.
Temperatures will be around 10 degrees above normal Thursday and between 15 and 25 degrees higher than the average on Friday, said National Weather Service meteorologist Robbue Munroe.
A fire weather watch, indicating a potential for critical wildfire conditions, will be in force from late Thursday evening through Saturday afternoon in the San Gabriel Mountains in L.A. and Ventura counties as well as the Santa Monica Mountains and the Santa Clarita valleys.
“A significant heat wave is expected to affect Southwest California Thursday through Sunday,” according to a National Weather Service statement. “The peak of the heat wave will be Friday and Saturday when widespread record-breaking triple-digit heat is expected. This heat in combination with single-digit humidities and gusty north winds will bring the potential for critical fire weather conditions across the (San Gabriel) mountains, Santa Barbara south coast, Santa Clarita Valley, and Santa Monica Mountains.
“In addition, the extreme heat will create an unstable air mass that will be capable of producing large vertical plume growth with any new fire ignitions, especially in the mountains and foothills.”
Forecasters said north winds of 20-30 miles per hour accompanied by 45-mph gusts would sweep the San Gabriels, with the strongest winds expected through the Interstate 5 corridor Friday into Saturday morning.
Humidity levels will dip to between 3 and 10 percent Friday, increasing to 7-15 percent Saturday. At the same time, highs of 100-110 degrees are expected Friday and 98-108 Saturday.
“A fire weather watch means that there is the potential for critical fire weather conditions. This, in combination with dry fuels, could create extreme fire danger and/or fire behavior,” warned the statement. “If fire ignition occurs, there could be rapid wildfire spread and large vertical plume growth that would lead to a threat to life and property.”
The NWS also issued an excessive heat watch scheduled to be in effect in L.A. County from Friday morning through Saturday evening, when heat records are likely to be set, according to an NWS statement, which said temperatures would be 82-92 right along the coast, 95-105 inland near the coast, 105-112 in the valleys, and 97-107 in the mountains.
In Orange County, an excessive heat warning will be in force from 10 a.m. Friday to 9 p.m. Saturday along the coast and in inland areas as well as the Santa Ana Mountains and foothills.
Libraries and municipal facilities such as recreation centers, senior centers and museums can serve as cooling centers for the public during normal hours of operation. Find your nearest facility at laparks.org/reccenter, laparks.org/scc or lapl.org/branches.
The NWS attributed the heat wave to a strong upper level high pressure system, causing heat to build significantly across Southwestern California.”
Inland Orange County is expected to be between 102 and 110 Friday and 94 to 102 Saturday while coastal areas will experience temperatures of 94-102 Friday and 88-96 Saturday. In the Santa Anas, highs will be between 98 and 108.
These conditions will increase the potential for serious heat-related illnesses, especially for the young and elderly, those performing outdoor activities, as well as those without access to air conditioning.
Forecasters urged members of the public to avoid strenuous activity in the heat, wear light weight and loose-fitting clothing, and drink plenty of water.
Most important, children, seniors and pets should never be left in a vehicle parked in hot weather, even with windows cracked open, since interior vehicle temperatures can quickly turn lethal, forecasters said, adding that the high heat also creates an increased potential for power outages.
Also issued by the NWS and scheduled to be in effect from 8 Thursday evening to 8 p.m. Friday in L.A. County is a high surf advisory. Surf of 5-7 feet is expected, with sets of up to 9 feet Thursday and Friday as a result of a large southerly swell generated by Hurricane Fabio.
In Orange County, a high surf advisory will be in effect until 9 p.m. Friday. Surf of 5-8 feet is expected, with occasional 10-foot sets.
In L.A. and Ventura counties, “strong and frequent rip currents are certain, and sneaker waves will be possible,” along with minor coastal flooding, according to the statement.
“There is an increased risk for ocean drowning. Rip currents can pull swimmers and surfers out to sea. Large breaking waves can cause injury, wash people off beaches and rocks, and capsize small boats near shore,” but “no significant damage is expected.”
“A High Surf Advisory means that high surf will affect beaches … producing localized beach erosion and dangerous swimming conditions,” noted an NWS statement. “Swim near a lifeguard. If caught in a rip current, relax and float. Don’t swim against the current. If able, swim in a direction following the shoreline. Ifunable to escape, face the shore and call or wave for help.”
The NWS forecast partly cloudy skies in L.A. County Thursday and highs of 76 in Avalon; 78 at LAX; 86 in Downtown L.A.; 88 on Mount Wilson; 91 in Long Beach; 93 in San Gabriel; 94 in Burbank; 96 in Pasadena; 100 un Palmdale and Lancaster; and 101 in Woodland Hills. A sharp increase in temperatures is expected Friday, when the high is forecast to be 102 in downtown L.A., 109 in Pasadena, and 113 in Woodland Hills. A gradual cool down is expected starting Sunday,
Sunny skies are forecast in Orange County, along with highs of 73 in San Clemente; 76 in Newport Beach; 78 in Laguna Beach; 87 in Irvine; 88 in Anaheim; 89 in Fullerton; and 93 in Mission Viejo and Yorba Linda. Temperatures will rise around 10 degrees along the Orange County coast Friday but by up to 17 degrees in inland areas, then begin slowly climbing down Sunday.