Library and sheriff's station complex in Borrego Springs
The library and sheriff’s station complex in Borrego Springs, where temperature hit 93 degrees. Courtesy County News Center

Since when does Sacramento look chilly to San Diego? Even Phoenix is cooler.

On a day when the state capital basked in low-80s temps and the Arizona metropolis was 89 degrees at 5 p.m., an autumn heat wave pushed temperatures to summerlike extremes in the San Diego area for a second straight day Tuesday.

And this amid a Santa Ana weather pattern expected to generate heightened local wildfire hazards through the end of the workweek.

The hot spell, which began in earnest on Monday, led to unseasonable highs across much of the county Tuesday afternoon. Notable thermometer readings included 90 degrees at North Island Naval Air Station and in Oak Grove; 91 in Carlsbad; 93 in Borrego; 94 in Valley Center; 95 in Ramona and at San Diego International Airport; 97 at Brown Field, Gillespie Field and Montgomery Field airports; 98 in El Cajon; 99 in Poway; 101 in Santee; and 102 in Pala.

The oppressive swelter led to a record high at Oceanside Harbor, where the maximum mercury reading of 84 degrees eclipsed the old Oct. 22 milestone of 78, set in 2016.

The toasty conditions, extremely dry air and strong winds out of the east — with recorded gusts of up to 38 mph in the inland valleys and 47 mph in the East County highlands as of late morning — led the National Weather Service to issue a heat advisory effective through late afternoon and kept firefighting agencies on high alert across the region.

Following a slight cool-down and modestly improved humidity levels on Wednesday, the blustery Santa Ana pattern is expected to regain momentum. The forecast prompted the NWS to institute a “red flag” wildfire warning. effective from 5 a.m. Thursday to 5 p.m. Friday. The alert denotes potential for “critical fire weather conditions” across the San Diego area’s valleys and mountain locales.

Over the period, winds out of the east and northeast will hit speeds of 25-35 mph, with isolated gusts up to 60 mph, and daytime air-moisture levels will drop to 5-10 percent, with poor overnight recovery, forecasters advised.

The winds should become calmer late Friday, then return to their more typical and temperate orientation from out of the west by Saturday, according to the weather service. Thereafter, another cooling trend is expected to begin Sunday and continue into early next week, the federal agency reported.

Updated at 8:26 p.m. Oct. 22, 2019

— City News Service contributed to this report.