SAN DIEGO -- Temperatures will begin warming Monday throughout San Diego County as another high pressure system is expected to bring extreme heat to the deserts by midweek.
A high pressure system passing through Mexico will cause temperatures to warm through Wednesday, according to the National Weather Service.
Highs in desert areas could reach 114 on Tuesday and 117 on Wednesday, then temperatures will drop heading into the weekend, forecasters said. Temperatures in the inland valleys will reach the high 80s both days and the mercury could rise to 99 on Wednesday near the foothills.
The NWS issued an excessive heat warning that will be in effect from 11 a.m. to 8 p.m. Wednesday in the county deserts.
High temperatures Monday could reach 81 degrees near the coast and inland, 84 in the western valleys, 92 near the foothills, 94 in the mountains and 111 in the deserts.