The warning was issued for Apple and Lucerne Valleys, Coachella Valley, San Diego County Deserts and San Gorgonio Pass Near Banning.

The peak of the heat wave is expected Thursday and Friday, the National Weather Service said. While it’s brought hotter temperatures than in recent weeks, it is not particularly extreme in terms of all-time Southern California highs. “This is definitely more normal heat for this time of year,” Sam Zuber, an NWS meteorologist said.

Extreme heat across the U.S. Southwest will build on Wednesday and is expected to last for several days. In Southern California, there are major fire and health concerns.