The wildfires that raged across Northern California last month will cost insurers more than $1.1 billion, according to catastrophe modeler Impact Forecasting.

The Valley Fire, northwest of San Francisco, destroyed almost 2,000 homes, leading to at least $925 million in expenses for the industry and making it the third-most expensive in California history, according to a report Thursday from Impact. The sum for the Butte Fire, southeast of Sacramento, is more than $225 million.

“The severity of the September wildfires in California serves as a reminder of how costly the peril can be for the insurance industry,” Adam Podlaha, head of Impact Forecasting, said in a statement.

Total economic losses, which include costs not borne by insurers, will probably exceed $2 billion, helping to make 2015 the costliest year for wildfires in the U.S. since 2007, according to Impact, which is a unit of London-based insurance broker Aon Plc. That was the year when the Witch Fire struck California’s San Diego County.

Dry weather, high temperatures and gusty winds hampered efforts to contain the fires, resulting in at least six deaths. Throughout the U.S., wildfires burned more than 9 million acres (3.6 million hectares) this year through Sept. 29, more than triple the total in the same period of 2014, according to the National Interagency Fire Center.

Arkansas, Idaho and Oregon are among other states currently reporting fires, according to the center. Before this year, eight of the 10 costliest U.S. wildfires occurred in California, according to Property Claim Services data compiled by the Insurance Information Institute.

And, as Podlaha said in the statement, “the peak of the California wildfire season is just beginning.”