The National Weather Service is warning valley communities in San Bernardino and Riverside counties that temperatures are expected to reach up to 106 degrees. Weather officials have issued a heat advisory that will go into effect at 10 a.m. Wednesday and will remain until 8 p.m. Friday.

Triple-digit temperatures will arrive in parts of Southern California on Wednesday as a heat wave descends, exacerbating the woes of firefighters who already are batting a number of wildfires across the region.