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Excessive Heat Warning Issued For San Diego County

The sun shines bright in the sky over San Diego, July 30, 2018.
KPBS Staff
The sun shines bright in the sky over San Diego, July 30, 2018.

Hot conditions in San Diego County were forecast Sunday to continue before conditions gradually cool through midweek.

The National Weather Service issued an excessive heat warning Sunday until 9 p.m. for San Diego County deserts, mountains and valleys.

Extreme heat, low afternoon relative humidity of 5-15%, and gusty westerly winds was predicted to maintain elevated fire weather conditions along the desert slopes, through the passes and into some desert areas Sunday.

RELATED: Hot, Dry Conditions Forecast For San Diego County Mountains, Deserts

Strongest southwest to west winds of 25-35 mph with gusts of 45-55 mph and higher were likely in these areas, especially near the passes starting later Sunday afternoon and continuing through Monday evening, the NWS said. Near critical fire weather conditions may develop in these areas for several hours later Sunday into the evening.

The extreme heat Sunday, coupled with very dry fuels in the mountains, was predicted to increase the potential for plume-driven fire growth as well, forecasters said. Elevated fire weather conditions were expected to continue in these areas through Monday, although some cooling was expected.

Better cooling and slightly higher humidity will work a little farther inland Tuesday and Wednesday.

High temperatures in coastal areas Sunday were expected to be 69-94 degrees with overnight lows of 57-62. Western valley highs will be 82-87 and 94- 99 in the foothills with overnight lows of 58-65.

Mountain highs were expected to be 94-103 with overnight lows of 60- 70. Highs in the deserts will be 116-121 with overnight lows of 79-87.

RELATED: Heat Wave Blazes On In San Diego County

Low pressure approaching the California coast was predicted to amplify the onshore flow Sunday through Monday and gradually push cooling farther inland through the first half of the week, the NWS said.

Areas of low clouds and patchy fog will continue nights and mornings along the coast.

An upper trough was expected to develop and approach the California coast through Wednesday. An upper ridge was expected to rebuild late this week, especially next weekend.

"This supports hotter temperatures returning to inland areas next weekend into the following week," forecasters said. "However, it is not looking to get quite as hot as this recent heat wave with upper heights most anomalous over the Pacific Northwest."

Breezy northwest winds will occur each afternoon and evening Monday through Wednesday across the outer waters with gusts approaching 20 knots, with the strongest winds expected Tuesday and Wednesday.