According to an article by Brad Plumer, "this will be the 7th time in the last 12 years that Congress hasn't adequately funded federal firefighting programs. Since 2002, the Department of Agriculture, which runs the Forest Service, has had to pull at least $2.8 billion from other programs in order to fight fires — without always getting fully reimbursed by Congress. And the problem is only likely to get worse in the years ahead."
Moreover, "the US Forest Service and Department of Interior expect they'll have to pull $470 million from other accounts — including programs that are supposed to help prevent fires in the first place. That, in turn, could make future wildfires even worse."
The article goes on to cover the growing size ("wildfires in the western United States grew at a rate of 90,000 acres per year between 1984 and 2011") and costs—and how poorly the country is prepared for the future of fires in the country.
Plumer also mentions two pieces of potential legislation that could change the way the federal government funds fire suppression efforts. One is a bill in the House by Rep. Mike Simpson (R-ID) and Kurt Schrader (D-OR) that would set predictable firefighting and prevention budgets, and allot overruns on a given year from emergency disaster bills. The Obama Administration has also recently proposed a special fund for especially high fire costs.