SAN FRANCISCO – Residents in densely populated regions of California are urged to be cautious around fire sources as several conditions together significantly elevate the risk of fires on Monday and potentially worsen later this week.

Over 25 million of California’s 39 million residents will be under red flag warnings or fire weather alerts this week due to high temperatures, low humidity, and fierce winds, which could reach 80 mph in certain areas—winds strong enough to be classified similarly to a hurricane.

The National Weather Service stated on Monday, “Gusty easterly winds coupled with low humidity levels will create elevated to critical fire weather conditions over coastal regions of California from today through Thursday.’’

These offshore winds, referred to as Santa Ana winds in Southern California and Diablo winds in the Bay Area, have historically been responsible for toppling power lines and igniting wildfires, which can quickly spread in dry vegetation.

In a warning for Los Angeles and Ventura counties issued for Sunday night through all of Monday, the Los Angeles NWS office reported wind gusts in mountainous areas—often the hardest for firefighters to access—could vary between 55 to 80 mph.

The forecast also mentioned, “Stronger and more widespread Santa Ana winds are expected on Wednesday and Thursday.’

According to meteorologist Anthony Edwards from the San Francisco Chronicle, the offshore winds this week—the opposite of the typical pattern blowing from inland to the ocean—are among the strongest seen in years.

Edwards also indicated that winds at the highest peaks in the Bay Area could reach 70 mph, likely triggering preemptive power shutoffs by utility company PG&E, with even stronger winds anticipated in the Sierra Nevada foothills.

The Bay Area’s red flag warning is in effect from 11 a.m. Tuesday until early Thursday, with a reminder to “have an emergency plan should a fire ignite nearby.’’