An excessive heat warning denoting potentially deadly conditions will be in effect over vast areas of the Southland on Wednesday and Thursday as a result of the heat wave gripping the region.
Though the South Bay and other areas of the Southern California coast are not under an excessive heat warning, a hazardous weather outlook has been posted.
The excessive heat warning will be in effect from 11 a.m. Wednesday to 7 p.m. Thursday in the Santa Clarita and San Fernando valleys and the Los Angeles and Ventura county portions of the San Gabriel mountains.
The NWS forecast highs Wednesday of 76 in Redondo Beach; 71 in Avalon; 73 at LAX; 81 in Newport Beach; 87 in downtown L.A; and 91 in Long Beach.
Thunderstorms could develop in the afternoon and evening hours in mountain and desert areas, creating a risk of wildfire, the National Weather service warned. These could be largely dry thunderstorms—fire-sparking lightning not accompanied by rain, said NWS meteorologist Rich Thompson.
"Hot temperatures and increased humidity ... will combine to create dangerous conditions in the afternoons and early evenings" Wednesday and Thursday, according to an NWS advisory.
Also on tap today for San Fernando and Santa Clarita residents is air quality in the unhealthful range, according to the Air Quality Management District.
"Heat exhaustion is possible, especially if engaging in strenuous outdoor activities. This weather could be deadly for unprepared campers or hikers," according to an NWS advisory.
To guard against heat exhaustion or heat stroke, the NWS advised residents to schedule strenuous activities for early mornings or the evening, wear light, loose clothing, and drink plenty of water.
"To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air- conditioned environments," the advisory noted.
"Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency -- call 911."
This morning in the Angeles National Forest, rangers raised the fire danger level from high to very high, because of the high temperatures and dried- out brush. Despite the "very high" fire danger designation, campfires are permitted in developed campgrounds, and camp stoves are allowed in the backcountry.
NWS meteorologists said monsoonal moisture filtering in from the southeast would create the possibility of thunderstorms in the mountains and deserts, starting today.
"Given the hot and dry conditions, the possibility of thunderstorms will result in a heightened fire-weather risk," an advisory said.
Thompson said he expects any thunderstorm to be mostly dry today, wet and dry Thursday, and mostly wet Friday.
The Los Angeles Unified School District, meanwhile, sent a memo to school principals this week reminding them of the district's guidelines for coping with hot weather, a district spokeswoman said. They include:
- relegate physical activity to early morning hours when the temperatures are cooler;
- keep doors and windows closed in air-conditioned classrooms;
- keep an eye on students with specific health problems; and
- make sure students stay hydrated.