The Butte Fire in Amador and Calaveras counties increased to more than 50,000 acres in less than 48 hours after it started last week. The Valley Fire in Lake County doubled overnight to 40,000 acres early Sunday.
Extreme weather conditions and steep topography were factors in the rapid spread of the Butte Fire.
But Daniel Berlant with Cal Fire says the state's historic four-year drought was a factor in the Butte Fire and the Valley Fire.
"This year we have seen nearly 1,600 more wildfires than we would for the same time period in an average year," says Berlant. "And that's because the drought conditions allow for a simple spark, an ember, and any type of open flame to quickly ignite into a wildfire and spread very rapidly."
Cal Fire calls the growth of the Butte Fire "unprecedented."
The Valley Fire is the third large wildfire in Lake County since July.