Santee and the San Diego County inland valleys are under an extreme heat warning until 8 p.m. Friday, according to the National Weather Service in San Diego. The alert was updated Tuesday afternoon and warns of dangerously hot conditions across the valleys.

The Weather Service forecast for Santee calls for a high near 101 on Wednesday, 104 on Thursday and 105 on Friday. Forecasters said heat index values could reach 105 Wednesday and 108 Thursday, with overnight lows mostly in the 70s limiting relief from the heat.

The warning says heat-related illnesses increase significantly during extreme heat events. Residents are urged to drink plenty of fluids, stay in air-conditioned rooms, stay out of the sun and check on relatives and neighbors.

For Santee residents, the hottest stretch is expected during the middle and end of the workweek, with gradual relief beginning Saturday and temperatures closer to average by Monday. People working outside, older adults, children and anyone without reliable cooling should take extra precautions.