California’s raging wildfires are so bad that American International Group Inc. and Chubb Ltd. are deploying teams of specialists and former firefighters to spray retardants on homes. The season may soon rank among the industry’s most costly.

The latest blazes have killed at least 31 people and damaged thousands of structures. For insurers that could mean several billion dollars in losses, RBC Capital Markets analyst Mark Dwelle told clients in a note on Monday. Last year, 1.24 million acres burned across the state, generating $16 billion in costs for insurers covering homes and farms, or almost quadruple the amount in 2016, according to ratings firm A.M. Best.

Insurers are hoping to reduce potential damage from the Camp Fire in the northern part of that state and the Woolsey Fire, which is spreading around parts of suburban Los Angeles. Median home values there exceed $1 million, according to estimates from Trulia. There are also mansions, owned by celebrities such as Kim Kardashian and Kanye West, with private firefighters of their own.

“Our client base in California has been heavily impacted” by wildfires over the past year, Jerry Hourihan, president of AIG’s private client group, said in an interview. Every blaze is “seemingly more devastating.”

Even before the latest blazes, state regulators were growing concerned that coverage for fires is getting harder and more expensive for consumers, according to a report from California’s insurance department last year. More homes are being built in areas prone to wildfires, and climate change is creating conditions for blazes to spread faster, said Chris Folkman, senior director of product management at risk modeler RMS.

“Something is changing rapidly,” Folkman said. “There might not be the concept of the fire season anymore, because if these conditions persist, fire season could be anytime.”

AIG bolstered its wildfire protection unit after last year’s fires and has seen increased demand from homeowners for advice on prevention, according to AIG’s Stephen Poux, global head of risk management services and loss prevention in the private client group. Its recommendations include installing new ventilation systems that block out embers from fires.

Chubb, which partners with Wildfire Defense Systems Inc., said it employs methods such as setting up sprinklers to raise humidity in the area, making it less amenable to fire, according to Fran O’Brien, president of the company’s North America personal risk services division.

More takeaways from the wildfires:

Predictions vary as investors wait for insurers to issue loss estimates. Meyer Shields, an analyst at Keefe, Bruyette & Woods, said he expects insured losses to be below costs tied to incidents in October 2017. Janet Ruiz, the Insurance Information Institute’s spokeswoman for California, said claims from this year’s fires may be similar to last year’s. Both Shields and Ruiz emphasized that it’s too early to be certain. Meanwhile, insurers are starting payouts, Ruiz said. Some are handing out debit cards to affected residents for short-term expenses. Coverage costs matter. Wildfires are making it harder and more expensive for the state’s utilities find insurance. That led PG&E Corp. to use a niche market this year to help protect itself.