California’s busy fire season could escalate this week amid strong winds and a prolonged and punishing heat wave that will hit much of the state. Meteorologists are warning of “critical” fire danger as conditions grow increasingly flammable during the Fourth of July holiday week — when wildfire ignitions typically spike.
“It’s a pretty bad combination, honestly, to have a potentially record-breaking heat wave that starts off with dry north winds,” UCLA climate scientist Daniel Swain said in a briefing Monday. “We have extra fuel for the fires … now we’re going to really kiln-dry it this week. And as if that weren’t enough, this is of course the week of the Fourth of July holiday.”
Human-caused wildfire ignitions rise sharply around the holiday because of fireworks use and an increase in the number of people outdoors.
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Multiple days of 100 to 110 degree temperatures are forecast, along with nights in the 70s and 80s. In Redding, Calif., temperatures could hit 115 later this week. A “red flag” warning, which denotes conditions that could lead to fast-spreading fires, is in effect through Wednesday evening for the Sacramento Valley into the San Francisco Bay Area, where winds gusting to 40 mph are forecast to combine with soaring temperatures and very dry air day and night. While wildfire concerns are greatest in Northern California below 4,000 feet in elevation, fire danger is also high in the southern half of the state, which could stoke blazes harder to control.
“New large fires are highly likely this week,” fire meteorologists at the U.S. Forest Service in Riverside wrote in a forecast. “This is a serious fire weather event, in addition to a hazardous heat event for human health.”
Utility company Pacific Gas & Electric is considering cutting power to about 12,000 customers in 10 Northern California counties Tuesday morning to prevent its equipment from sparking wildfires during the wind event. The power shut-offs would create additional challenges for Californians coping with dangerous temperatures and who may also face heat-related power outages during the week.
Heat may ‘flip the switch’ on fire season
Fire danger across the state has been steadily increasing amid repeated heat waves over the last several weeks, with some spots in interior California recording their warmest June on record.
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So far this year, 131,483 acres have burned — an unusually high number for this early in the season. Thick grasses from two consecutive wet winters dried out quickly in June and have been driving the fast-spreading blazes. “We are seeing that the level of dryness has rapidly changed in recent weeks,” Swain said. “The vegetation moisture and flammability metrics are going to skyrocket in the coming days.”
This week could mark a turning point in the fire season toward blazes that are much more difficult to control, as shrubs and tree canopies become more likely to burn.
“The extended and near historical heat wave event for the time of year could ‘flip the switch’ in placing all of the fuel drivers into a flammable alignment below a certain elevation band,” Brent Wachter, a fire meteorologist with the Northern California Geographic Area Coordination Center in Redding, said in an email.
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Several large fires are already burning around the state, including the Basin Fire in the Sierra National Forest northeast of Fresno, which has spread more than 13,000 acres and as of Monday evening was 0 percent contained.
Fire risk could now be above normal in July
Meteorologists had initially expected a slower start to the California fire season, with lower risk into midsummer. But because of the persistent heat, the moisture benefits of this past wet winter have been fleeting in many areas.
Fire outlooks now indicate an “above normal” risk of large fires in California in July, mainly in the interior valleys, foothills and deserts. In fact, fire potential is expected to be high for much of the Western United States into September, from the southwest to the Pacific Northwest.
The intense heat is forecast to linger out West into mid-July, according to the Climate Prediction Center, with the region leaning warmer than normal through September.
California’s entry into the heart of fire season has happened “much earlier than anticipated,” and most areas away from the coast should remain “quite flammable for the remainder of the summer,” according to an outlook released Monday.
