A heat wave will roll into the Southland Monday, threatening to spark wildfires and make people ill.
A red flag warning signifying a high risk of wildfire arising from high heat, high winds, low humidity and bone-dry vegetation will be in force from 10 a.m. Monday in the Santa Clarita Valley, and from 4 Monday afternoon in the San Gabriel Mountains in L.A. and Ventura counties. Both will expire at 9 Tuesday night.
North winds of 10-20 miles per hour and gusting to 30 mph are expected in the Santa Clarita Valley amid 107-degree heat and humidity levels of 4-8 percent, while in the San Gabriels the wind is expected to blow at 15 to 30 miles per hour and gust to between 35 and 45 mph amid highs of around 100 degrees and humidity levels of 3-10 percent.
“If fire ignition occurs, conditions are favorable for very rapid fire spread, including … extreme fire behavior, which would threaten life and property,” warned an NWS statement.
The National Weather Service also issued an excessive heat warning from 10 a.m. Monday through 8 p.m. Tuesday.
“Summer is the main reason” for the heat, NWS Meteorologist Kathy Hoxsie said, pointing out that the last 10 days of July and the first 10 days of August rank among the hottest of the year.
The excessive heat warning will be in force from 10 a.m. Monday until 8 p.m. Tuesday in the Santa Clarita, San Fernando and San Gabriel valleys, the San Gabriel and Santa Monica mountains, coastal cities, metropolitan L.A. and the Hollywood Hills.
The NWS said in a statement that prevailing conditions create “increased 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.” They also create an “increased potential for power outages.”
Also scheduled is a wind advisory signifing winds or gusts of at least 35 mph. It will be in force in the San Gabriel Mountains until 3 a.m. Tuesday.
High pressure usually sits over Arizona and Southern California in the summer, shifting from Arizona to California and back, and this week it will be over Southern California, Hoxsie said. Sometimes the pressure just expands and both areas are affected, according to Hoxsie.
Tuesday is forecast to be the hottest day, Hoxsie said. Weather models indicate temperatures will begin to drop a few degrees Wednesday but Hoxsie said it could remain warm instead and drop off Thursday.
The weather service and law enforcement caution that those who work outdoors should avoid the midday sun, wear light, loose-fitting clothing and drink plenty of water.
Avoid leaving senior citizens and kids at home without air conditioning, if possible. And never leave a child, a senior or a pet in a parked vehicle, even with windows cracked open, because interior temperatures in vehicles parked in the heat quickly can turn lethal.
The NWS forecast a mixture of sunny and partly cloudy skies in L.A. County Monday and highs of 83 degrees in Avalon and at LAX; 91 in Long Beach; 92 on Mount Wilson; 94 in Downtown L.A.; 99 in Burbank; 101 in Pasadena and San Gabriel; 103 in Lancaster; 104 in Saugus and Palmdale; and 107 in Woodland Hills. Tuesday’s temperatures will be slightly higher. A decline of a few degrees is expected Friday.
In Orange County, the NWS forecast sunny skies and highs of 79 in San Clemente; 83 in Newport Beach and Laguna Beach; 92 in Irvine; 95 in Fullerton and Anaheim; 96 in Mission Viejo; and 98 in Yorba Linda.