Wildfires across Washington state grew to more than 300 square miles Saturday, officials said, making it the largest group of wildfires in state history.

Four fires, sparked by lightning July 14, have burned at least 336 square miles of forest and grass in the northwest part of the state, increasing from 260 square miles Friday. The Okanogan county sheriff’s office said Saturday 80 to 100 structures have been lost so far and 300 to 500 homes have been evacuated as the fires blacken hillsides and grassy pastures.

High winds and hot weather have made containing the blaze difficult, and changed evacuations and road closures rapidly. As many as 3,000 people were without power Saturday due to damaged lines. Returning power to rural towns could take as long as two weeks.

The National Guard has deployed six helicopters to drop water on the fires and has 100 soldiers on stand-by.

So far, there have been no reports of deaths or serious injuries.