The advisory is in effect until 2 p.m. today, the National Weather Service said.
Temperatures today will be 81 degrees in San Bernardino, 82 in Redlands and 84 in Ontario, according to Accuweather.
High temperatures on Thursday could reach 77 degrees in San Bernardino and 78 in Ontario and Redlands.
Reach Melissa via email or call her at 909-386-3878.
Get the latest crime and public safety news on Twitter @IECrime.