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.

Temperatures are expected to reach triple digits in parts of the Inland Empire on Wednesday, parts of L.A. and Orange counties by Thursday

Denver Public Schools will close or release students early on Thursday from over a dozen campuses due to extreme heat and lack of air conditioning.

Denver Public Schools will close 13 of its schools Thursday because of anticipated “extreme heat,” the district announced. The National Weather Service is forecasting a high near 99 degrees in the Denver area Thursday.

A fire weather watch was issued for Thursday, Aug. 21, while an extreme heat watch was issued for Aug. 22-24 for Eugene and Springfield.

L.A. County is warning residents to prepare for a severe heatwave and take protective measures against heat-related illnesses.