All evacuation orders have been lifted in Paradise, more than a month after a wildfire devastated the entire town.
At least 86 people died and more than 14,000 homes were destroyed in the northern California town.
It will be the first time many residents will see their properties since the fire broke out on November 8.
The Butte County health officer issued an advisory strongly urging people not to live on destroyed property until it is declared clear of hazardous waste, ash and debris.
The county is providing masks, gloves and protective suits to reduce exposure to toxic materials.
California wildfires
Authorities also warned of an increased risk of flash flooding in the burn areas.
Just a day after the fire began, the blaze grew to nearly 140 square miles with firefighters struggling to contain it.
For the first few days, fire crews were forced to stop trying to tackle the flames and instead help get people out.
People reported seeing much of the community go up in flames, including homes, supermarkets, businesses, restaurants, schools and a retirement centre.
Rural areas fared little better. Many homes have propane tanks that were exploding amid the flames.
Animals rescued from California wildfires
All evacuees had harrowing tales of a slow-motion escape from a fire so close that they could feel the heat inside their vehicles as they sat in a terrifying traffic jam.
Fire surrounded the evacuation route, and drivers panicked. Some crashed and others left their vehicles by the roadside.
"It was just a wall of fire on each side of us, and we could hardly see the road in front of us," police officer Mark Bass said.
Additional reporting by AP.
