No doubt about it, firefighters say. It's getting hotter.

Wildland firefighters usually cite three main reasons for the recent increase in large, costly fires.

In addition to the buildup of brush and small trees from a century of successful fire suppression, there's also dryness and heat.

A drought that has gripped the West on and off for more than a decade has dried out many of the forests.

Firefighters interviewed for this series said that the climate is changing, and said they are seeing longer, hotter fire seasons.

“I'm no scientist. I'm the fire guy. But we know that fire seasons are longer,” said Tom Harbour, head of fire and aviation management for the U.S. Forest Service.

Rick Trembath of Montana has fought wildfires for 49 years, and he notices the change.

“You can say what you want about climate change, but it has been a little hotter and drier in some areas of the country,” Trembath said.