How much will the California wildfires cost? Here's why that's a tough question.

More than 82,000 people have been evacuated from their homes since Tuesday morning as a wildfire broke out in San Bernardino, California, and spread through the surrounding mountains.

"It hit with an intensity that we hadn't seen before," San Bernardino County Fire Chief Mark Hartwig told the Associated Press.

Spending on wildfires has been on the rise. The California Department of Forestry and Fire Protection spent $336 million fighting wildfires in 2015 and 2016, up from $209 million the year before. 

This July alone, spending was roughly $53 million, the Pasadena Star-News reported.

It's hard to calculate exactly what the total cost of this year's wildfires will be. One 2015 report from the federal Department of Agriculture found that the combination of climate change and increasing development means fire seasons are getting longer and more costly. 

Fire season is 78 days longer than it was in 1970, and spending on fires has increased from 16% of Forest Service's annual budget in 1995 to more than half that budget in 2015, according to the report. 

And that's just the cost of fighting the actual fires. Additional costs, including damage to homes and infrastructure, insurance payouts, re-seeding, losses in tax revenues and declining property values are all increasing and hard to put a precise figure on. 

One 2009 study of San Diego County found that these costs might be much more dire, and that actual firefighting accounts for less than 2% of the total economic impact of wildfires.

We won't know the total cost of this year's fires for some time, but it already seems safe to say that the $336 million figure might be just a drop in the bucket. Based on the above study, even a conservative estimate of the total economic impact would be well into the billions.