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.

The peak of a heat wave lingering over Southern California is expected on Thursday, which could bring record-breaking temperatures to some areas.

The peak of the heat wave is expected Thursday and Friday, the National Weather Service said. While it’s brought warmer 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.