Temperatures surpassed 100 degrees in the San Fernando, Santa Clarita and Antelope valleys on Wednesday, but a gradual cooling trend is forecast to begin Friday, according to the National Weather Service.
A high pressure system pushed temperatures to 105 in Woodland Hills and
Saugus, 104 in Chatsworth, 103 in Northridge, 101 in Van Nuys and 111 in
2003, according to the National Weather Service.
Some portions of Los Angeles County were spared the extreme heat. The
temperature of 87 in downtown Los Angeles was two degrees above the norm of 85 for this time of year, while it was 70 at Los Angeles International Airport.
Thursday's National Weather Service forecast calls for highs of 93 to 105 in the San Fernando Valley, 96 to 106 in the Santa Clarita Valley and 97 to 104 in the Antelope Valley.
Studio City will see a high of 94 on Thursday.
There is a slight possibility of what the National Weather Service called somewhat rare nighttime summer thunderstorms over the coast and valleys of Los Angeles County Thursday night because of the combination of an upper level disturbance moving over the coastal waters, plenty of mid-level monsoonal moisture and an unstable atmosphere.
Thunderstorms will also be possible Thursday night in the Antelope Valley, the mountains of Los Angeles County and in and around Catalina Island.
Any thunderstorms that develop Thursday night would likely be accompanied with gusty winds and frequent lightning. Rainfall may be limited due to a dry layer at lower levels of the atmosphere.
The high pressure is forecast to weaken beginning Friday and a trough of low pressure will be moving in, according to the National Weather Service.
An excessive heat warning, signifying dangerously hot weather, has been issued by the National Weather Service for the deserts and the San Fernando and
Santa Clarita valleys through Thursday night.
"Heat exhaustion is possible, especially if engaging in strenuous outdoor activities. This weather could be deadly for unprepared campers or hikers," the NWS warned.
"Anyone overcome by heat should be moved to a cool and shaded location. Heat stroke is an emergency -- call 911."
To guard against heat exhaustion or heat stroke, people should limit strenuous exercise to the early morning or the evening, wear light, loose clothing, and drink plenty of water.
In the Angeles National Forest, rangers raised the fire danger level from high to very high this morning, 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.
Thunderstorms, possible through Friday, also could trigger wildfires caused by lightning strikes.
The Los Angeles Unified School District, meanwhile, distributed a memo to school principals this week reminding them of the district's guidelines for coping with hot weather. 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
- make sure students stay hydrated.