Cooler temperatures and rain are expected to provide much-needed help in the fight against massive fires roaring through northern California, officials said Wednesday.

The rainfall will offer a reprieve for thousands of firefighters battling two major wildfires -- the Valley Fire and the Butte Fire -- that erupted over the weekend, killing one person, destroying 700 homes and displacing thousands.

"With cooler weather and the rain in the forecast, that should aid firefighters on the fire line today," Cal Fire field battalion chief Mike Smith told AFP.

"We are trying to make as much progress today as we can because a different weather pattern is supposed to move in tomorrow.

"Heat is expected to return, along with wind, and that could change the situation."

The Valley Fire, described as the most destructive to hit the drought-stricken western United Sates, has charred more than 70,000 acres (28,000 hectares) -- an area almost three times the size of Paris -- destroyed 585 homes and displaced 13,000 people, fire officials said.

The fire by Wednesday morning was 30 percent contained while the Butte Fire, which burned nearly 72,000 acres, was 40 percent contained.