San Diego heat wave peaks Wednesday, Thursday but hot weather expected through mid-July 

SAN DIEGO (FOX 5/KUSI) -- The heat is officially on as heat alerts for all inland locations kicked in the middle of the week.

As of 2 p.m., inland valley locations such as El Cajon, Ramona and Escondido, and mountains communities like Julian and Pine Valley reached the low 90s while deserts like Borrego Springs sat at a sweltering 117 degrees. 

A Heat Advisory is in effect for valleys and mountains where afternoon temperatures are expected to peak in the upper 80s to mid 90s Wednesday and Thursday, marking above average conditions for the next few days. In the deserts, an Extreme Heat Warning is active until 8 p.m. Thursday as temperatures are forecast to be as high as 118 degrees for a second day. 

Surface high pressure expanding from the southeast is powering our first significant heat wave of the summer and bringing above average conditions for the entire region. The heat dome of sinking hot air really doesn't look like it will move over the next week. Daytime highs will drop a few degrees into the weekend, but shoot back to warmer than normal by July 14. 

The heat is bringing elevated fire risk to the region as conditions continue to dry out. As the heat dome is expected to shift slightly more west next week, it could mean record hot temperatures even for the coast as the marine layer thins out. 

For Thursday, daytime highs at the coast will top out in mid 70s with upper 80s to mid 90s for the valleys and mountains and between 114 and 118 degrees for the deserts. 

By Saturday, daytime highs look to drop about 5 - 10 degrees for most locations with a little bit more cloud cover along the coast and coastal valleys for the weekend morning and evenings.