A man runs with his dog as a surfing class enters the ocean during a heatwave in Oceanside. REUTERS/Mike Blake

An excessive heat warning has been issued for parts of San Diego County from 11 a.m. Thursday until 8 p.m. Friday, according to the National Weather Service.

Dangerously hot conditions with temperatures up to 118 are expected in the San Diego deserts and Borrego Springs.

The NWS warns extreme heat can significantly increase the potential for heat-related illness, particularly for those working or participating in outdoor activities.

Overnight temperatures will be above normal and warm with temperatures expected to be in the mid 80s to lower 90s. Friday is expected to be the hottest day, with temperatures on Saturday beginning to drop. Monsoonal moisture and conditions are expected to increase on Saturday.

The NWS recommends drinking plenty of fluids, staying in air conditioned areas, and staying out of the sun.

–City News Service