LOS ANGELES—Summer’s over, but Mother Nature will turn up the heat in parts of the Southland Tuesday, with “dangerously hot temperatures” possible in some areas, along with increased risk of wildfires.

Forecasters said temperatures will increase Tuesday and again Wednesday, leading to the potentially dangerous weather conditions over that span before a cool-down begins Thursday.

Record high temperatures have already been reported in Lancaster, Palmdale, and Sandberg. It was 100 in Lancaster on Monday, tying the record for the day set in 2001. Temperatures reached 100 at Palmdale Airport, breaking the record for the day of 99 set in 1980. It was 91 in Sandberg, tying the record for the day set in 1980.

Excessive heat warnings will be in place from 11 a.m. Tuesday until 8 p.m. Wednesday in the Santa Clarita and San Fernando valleys, where temperatures could reach 108 degrees. In the Western San Gabriel Mountains and Interstate 5 and 14 freeway corridors, highs could potentially reach 104 degrees, according to the National Weather Service.

A red flag warning of critical fire danger conditions will be in effect from 9 a.m. Tuesday until 8 p.m. Thursday for the western Dan Gabriel Mountains and 14 Freeway corridor, thanks to the anticipated heat, gusty northeast winds and low humidity.

Less severe heat advisories will be in place from 11 a.m. Tuesday until 8 p.m. Wednesday in the San Gabriel Valley, the Santa Monica Mountains Recreational Area and eastern San Gabriel Mountains, where temperatures will flirt with the triple-digit mark.

Heat advisories that had been issued for parts of the Antelope Valley were canceled, although “moderate heat impacts are still expected Tuesday and Wednesday,” forecasters said.

Although temperatures are expected to back off by Thursday, roughly falling 3 to 6 degrees, forecasters said there is a chance the threat of potentially dangerous heat could persist in some areas.

In areas under the threat of excessive heat, forecasters repeated their standard warning for people to be on the lookout for signs of heat illness, particularly in “the very young, the very old, those without air conditioning and those active outdoors.”