Southern California was feeling the effects of a mini heat wave, with temperatures expected to climb about 5 to 10 degrees above area norms Wednesday and Thursday.

The heat spell was forecast to peak Wednesday and Thursday, ahead of some weekend cooling, followed by another bout of above-average temps early next week, according to the National Weather Service.

Wednesday’s high in downtown Los Angeles is expected to be 88 degrees, with Pasadena expected to reach 91, Van Nuys expected to hit 93, Santa Clarita slated for 95 and Lancaster and Palmdale both expected to hover around 100 degrees.

Nearly identical numbers are forecast for Thursday.

The culprit, according to the NWS, was a high-pressure system over Arizona that’s expanding westward into Southern California.

“Weakening onshore flow and subsidence aloft from the strengthening high pressure system will squash the marine layer to under 1,000 feet by Wednesday and bring significant warming to inland areas and minor warming to coastal areas,” the NWS said.

Nighttime temps will mostly be in the 60s throughout the mini hot spell.

Fire conditions were “seasonably elevated” into early next week — with brief “critical fire weather conditions” in interior regions.

The hot, dry conditions are making the area more prone to fire starts, borne out by three relatively minor brush fires that broke out in Riverside County on Monday.

An extreme heat warning was in effect Wednesday for the Coachella Valley and San Gorgonio Pass near Banning, where temperatures could potentially reach as high as 118 degrees.

The warning issued by the NWS will be in place until 8 p.m. Thursday, with forecasters issuing the traditional warnings for people to drink lots of fluids, seek out air conditioning and check on relatives and neighbors who might be susceptible to heat illnesses.

Riverside and San Bernardino county valleys and mountains will be under a less severe heat advisory until 8 p.m. Thursday, with temperatures of up to 105 degrees possible in the valleys and into the 90s at mountain elevations below 5,000 feet.

Temperatures across the inland areas were expected to be 5 to 10 degrees above normal Wednesday and Thursday. But the heat wave is expected to be short-lived, with temperatures falling about 4 to 8 degrees in many areas on Friday, when highs will range from the upper-80s to upper-90s in the Inland Empire, and up to 114 degrees in the lower deserts.

As always, health officials warn that, during heat waves, people should take precautions such as limiting outdoor activities, seeking out shade and staying hydrated.

Pets should also be kept in shady areas and given ample water. In addition, the public is reminded to never leave children or pets unattended in vehicles for even a minute, as the interior of vehicles can quickly reach lethal temperatures.

Los Angeles Mayor Karen Bass urged residents to take advantage of city locations that offer air-conditioning for people to escape the heat, such as recreation centers, municipal pools and libraries. A listing of available recreation centers is available at laparks.org/reccenter, while library locations are available at lapl.org/branches.

Residents can search for cooling centers near them at https://lahub.maps.arcgis.com/apps/instant/nearby/index.html?appid=d3bea5218c3b 4adca485a32c9e3fabee.