WENATCHEE, Wash. — Firefighters battled stubborn blazes that kept residents from homes in Montana, Wyoming and Washington as authorities worried the weather could worsen the volatile situation.

High temperatures, lower humidity and greater instability increase the potential for fires to grow, said Ed Delgado, the national predictive services meteorologist for the National Interagency Fire Center in Boise, Idaho.

"Our biggest concern right now is existing fires," he said. "We're not expecting lightning over the next few days, although that doesn't alleviate the potential for human-caused fires, especially as we get into camping and hunting seasons."