SAN DIEGO -- Scorching temperatures are expected in the San Diego County deserts Wednesday and the rest of the county will remain hot before cooling off heading into the weekend.
The National Weather Service issued an excessive heat warning that will be in effect from 11 a.m. to 8 p.m. Wednesday in the county deserts.
The warnings of high heat came as students returned to school in some major districts around Southern California, including Poway Unified. About 37,000 students returned to class at the district's 39 campuses, and parents were warned to dress their kids in layers in expectation of hot recess and lunch periods.
A high pressure system currently centered off the southwest coast will be replaced by a trough of low pressure moving inland on Thursday, but until then temperatures will remain hot, NWS meteorologist Stefanie Sullivan said.
High temperatures Wednesday could reach 85 degrees near the coast and inland, 89 in the western valleys, 99 near the foothills, 101 in the mountains and 118 in the deserts.
The NWS advised that those who work outdoors should avoid the midday sun, wear light, loose-fitting clothing and drink plenty of water.
Nighttime lows will be in the high 70s to low 80s until Thursday in the deserts, meaning the minimal cooling at night could pose a health risk to those who don't have access to air conditioning because the body needs time to cool down from the day's heat, according to the NWS.
The combination of hot days and warm nights is expected to increase the threat of heat illness, and the NWS urged residents to drink plenty of fluids, stay out of the sun and check up on relatives and neighbors.
Temperatures will decrease significantly heading into the weekend, with highs in the deserts expected to drop from 118 to 115 on Thursday and 111 on Friday.