LIVE VIDEO: Presidential debate between Donald Trump and Hillary Clinton

Red flag warning extended through Thursday evening

SAN DIEGO — An intense summer heat wave kept the San Diego area sweltering for a fourth straight day Tuesday, heightening wildfire risks in mountain and desert communities.

The unrelenting hot spell, combined with stiff, gusty winds and low humidity levels, prompted the National Weather Service to extend a previously issued “red flag” wildfire warning by 24 hours, until 9 p.m. Thursday. The alert indicates imminent potential for “extreme fire behavior.”

High temperatures this afternoon are expected to range from 77 to 82 degrees along the coast, 87 to 92 inland, 91 to 96 in the western valleys, 96 to 101 near the foothills, 93 to 99 in the mountains and 109 to 114 in the deserts, the NWS advised. Winds of 25 to 30 mph, with gusts of up to 40 mph, are possible in the deserts and mountains.

On Monday, the heat wave pushed afternoon temperatures into the 80s and 90s along the coast, the 90s to 105 in inland areas, the low to mid-90s in the East County highlands and up to 113 in the local deserts, according to the NWS. It also led to a heat record in Alpine, where the high of 102 degrees surpassed the prior Aug. 15 milestone of 101, set last year. El Cajon’s maximum mark of 103 matched its previous record for the date, also logged in 2015.

Authorities advised the public to guard against potentially serious heat- related ailments by staying hydrated; avoiding unnecessary outdoor labor; checking on neighbors and relatives, especially the elderly; and making sure to never leave children, seniors or pets in parked cars, which can quickly become death traps when temperatures are high.