Winds and lightning added to the dangers for crews battling the nation’s largest wildfire Monday in dry Oregon forests, just one of dozens burning across several Western states.

The destructive Bootleg Fire, one of the largest in modern Oregon history, has burned more than 476 square miles. The blaze just north of the California state line was 25 percent contained.

Meteorologists predicted critically dangerous fire weather through at least Monday with lightning possible in California and southern Oregon.

“With the very dry fuels, any thunderstorm has the potential to ignite new fire starts,” the National Weather Service in Sacramento, California, said on Twitter.

Thousands of people have been ordered to evacuate, including some 2,000 people who live in rugged terrain among lakes and wildlife refuges near the fire, which has burned at least 67 homes and 100 outbuildings while threatening many more.

Climate change has made the West much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive. Firefighters said these conditions in July are more typical of late summer or fall.

A growing wildfire south of Lake Tahoe jumped a highway, prompting more evacuation orders, the closure of the Pacific Crest Trail and the cancellation of an extreme bike ride through the Sierra Nevada mountains.

The Tamarack Fire, which was sparked by lightning July 4, had charred about 28.5 square miles of dry brush and timber as of Sunday night. The blaze was threatening Markleeville, a small town close to the California-Nevada state line. It has destroyed at least two structures, authorities said.

About 800 fire personnel were assigned to battle the flames by Sunday night, “focusing on preserving life and property with point protection of structures and putting in containment lines where possible,” the U.S. Forest Service said.

Overall, about 70 active large fires and complexes of multiple blazes have burned nearly 1,659 square miles in the United States, the National Interagency Fire Center said. The U.S. Forest Service said at least 16 major fires were burning in the Pacific Northwest alone.