Southern California will enter a dangerous and prolonged heat wave Friday, with temperatures reaching triple digits in some areas and extreme heat expected to persist through next week.
The National Weather Service issued an Extreme Heat Warning from 10 a.m. Friday through 8 p.m. Thursday for coastal and valley areas of Los Angeles County.
Temperatures could reach 90 degrees along the coast and 105 degrees in the valleys during the warning period, according to the NWS.
Friday is expected to bring temperatures 10 to 15 degrees above normal, with highs in the mid- to upper 80s across most coastal areas and the lower to mid-90s along parts of the Los Angeles County coast. Valley temperatures are expected to range from the upper 90s to 105 degrees.
“The well advertised long duration heat wave kicks off on Friday,” according to the NWS.
Saturday is expected to be the hottest day of the next seven, with temperatures rising another 2 to 4 degrees in coastal and valley areas and locally as much as 6 degrees, forecasters said.
Most coastal areas are expected to reach the 90s Saturday, while valley temperatures could range from 100 to 107 degrees, or about 15 to 20 degrees above normal.
“This will make Saturday the hottest of the next 7,” according to the NWS.
The heat is expected to ease only slightly Sunday, with temperatures remaining generally 10 to 15 degrees above normal Monday through Wednesday. Above-normal overnight temperatures could also limit relief from the daytime heat, forecasters said.
Extreme Heat Warnings will also be in effect from 10 a.m. Friday through 8 p.m. Thursday for coastal and inland Orange County.
High temperatures in coastal Orange County are expected to range from the mid-80s to around 90 near the coast and reach the lower to mid-90s near higher coastal terrain, according to the NWS. Inland Orange County highs are expected to range from the mid-90s to near 100.
Overnight lows in both coastal and inland Orange County are expected to remain mostly in the lower to mid-70s.
“Even through this heat wave will not likely produce record heat it will still be very dangerous due to the prolonged duration of the event,” according to the NWS. “The relentless heat will have a hazardous wearing down effect on people, (especially) the very young and old.”
Humidity is expected to increase Monday through Wednesday as moisture from Hurricane Rachel moves into the region, with a 5% to 15% chance of afternoon showers or thunderstorms in the mountains, according to the weather service.
Forecasters said the latest long-range models indicate conditions could begin improving around Oct. 10.
The NWS advised residents to drink plenty of fluids, stay in air-conditioned areas, avoid the sun and check on relatives and neighbors during the heat wave. Residents were also urged not to leave children or pets in unattended vehicles because interiors can reach lethal temperatures within minutes.