Why is California so hot? Here's why temperatures are remaining high this weekend

High temperatures continue to scorch Californians across the state Friday.

Dozens of cities in Southern California reached 90 degrees and above just before 6 a.m., the National Weather Service San Diego posted on social media.

It comes amid days of excessive heat warnings plaguing regions throughout the state and at least one city breaking a heat record.

That unfortunate title goes to Indio, which reached 121 degrees on Sept. 5 , beating its previous record by one degree set in 2020, according to the NWS San Diego.

What is causing this heat?

The primary reason Californians have been suffering from heat is an upper-level ridge or an upper-level high-pressure system over Southern Nevada and Southern California, said Dave Munyan, a meteorologist with the NWS San Diego.

In simplified terms, these ridges allow air to collect and sink. Munyan explained that there is a relationship between pressure and temperature, and the air heats up as it compresses. Hotter weather is generally seen under these ridges, spanning multiple states.

The ridge started “really strengthening” Thursday and will continue through Friday and linger through the weekend. It has refused to weaken and move from our area, he said. It’s why people checking the weather forecasts for the week may have seen a slight uptick in their Sunday, even Monday, temperatures, Munyan said.

What is the weather right now?

High temperatures continue throughout California on Friday and through the weekend, bringing with it excessive heat warnings and other heat advisories. Here are just some of the triple-digit temperatures forecasted across the state, according to various NWS offices in California:

• A portion of southwest California, including Santa Clarita, Thousand Oaks, Burbank, and East Los Angeles, is under an excessive heat warning through Monday evening, facing temperatures up to 115 degrees.
• The Western San Fernando Valley remains under an excessive heat warning through Monday evening, with highs up to 118 degrees. The Inland Empire, also under an excessive heat warning through the same period, can see temperatures of 102 degrees or soar up to 114 degrees.
• A portion of central California, including Bakersfield, Tulare, Merced, and Fresno, is under a heat advisory through Saturday evening. Temperatures will be between 102 and 107 degrees.
• Sacramento, Redding, Stockton and other cities in the Carquinez Strait and Delta, Sacramento Valley, northern San Joaquin Valley and surrounding foothills are under a heat advisory through Friday evening and will see temperatures between 100 and 109 degrees through Friday evening.
• The Coachella Valley and San Diego County deserts are also under an excessive heat warning Friday, with highs between 112 degrees and 120 degrees forecasted.

When does the heat end?

A cooling trend will bring temperatures back to near-average next week, NWS San Diego posted on social media, and deserts will start to get some moisture back — the first sign that things will get better, Munyan said.

A drier monsoon season has contributed to how easily it’s warmed up, he said. A moister air mass is harder to heat up (and cool down) than a more dry air mass, he said.

Paris Barraza is a trending reporter covering California news at The Desert Sun. Reach her at pbarraza@gannett.com. Follow her on Twitter @ParisBarraza.

This article originally appeared on Palm Springs Desert Sun: Why is California so hot? Here's why temperatures are remaining high this weekend