dog heat
A dog cools off in a kiddie pool. Photo via @sdhumane Twitter

Dangerously hot conditions have prompted the National Weather Service to issue an excessive heat warning for the deserts and other parts of San Diego County Thursday.

The excessive heat warning is in effect until 8 p.m. Friday with temperatures expected between 112 and 117.

In the valleys, Escondido, El Cajon, San Marcos, La Mesa, Santee and Poway, a heat advisory will be in effect until 8 p.m. Friday. High temperatures are expected to reach 100 degrees.

The dangerous heat wave continues to grip parts of San Diego County this week and will remain through the weekend. The coast will be the only place to find relief from the heat with highs predicted in the 70s.

Highs Friday are forecast to be 74 to 79 near the coast, 82 to 85 inland, 85 to 90 in the western valleys, 95 to 100 near the foothills, 93 to 103 in the mountains and 112 to 116 in the deserts, according to the weather agency.

“Extreme heat will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities,” NWS forecasters warned. “Know the signs and symptoms of heat exhaustion and heat stroke. Wear light weight and loose fitting clothing when possible and drink plenty of water.”

Gradual cooling is expected to begin Sunday with the most significant drop in temperatures on Monday, forecasters said.

City News Service contributed to this article.