Schulz's widow Jean, 78, was evacuated from their split-level home in Santa Rosa on Monday shortly before the fire reduced it to rubble, Monte Schulz told CNN. She is safe and staying with family, he said.
"The things that they lost in there are irreplaceable," said Monte Schulz. "It's not just the memorabilia. It's that life that my stepmother had with him. It's completely gone."
Charles and Jean Schulz moved into their hillside home in Santa Rosa in the late 1970's, his son said. The cartoonist died in his home in 2000.
Charles Schulz remains a beloved figure in the Santa Rosa community.
The Sonoma County Airport is named after him and carries a logo of Snoopy flying while sitting on top of his dog house.
The Charles M. Schulz Museum and Research Center is located in the city, which stores many of his illustrations, and celebrates the cartoonist and his characters, including Charlie Brown and Snoopy.
The museum was unharmed in the wildfires, said Tracey Pugh, the museum media relations director. But it is closed due to a lack of power and there is no set date for re-opening the facility.
"While we are grateful our building was spared our hearts go out to those members of our community that were less fortunate," according to a notice on the museum's website.
"Our thoughts are with everyone affected and we look forward to working with local organizations and businesses when we reopen to determine how best to give back to our community."
Another member of the Schulz family was also affected by the wildfires this week.
Monte Schulz's brother Craig Schulz, who has lived in Santa Rosa since 1978, also lost his family home to the wildfires.
"The only thing Craig has at this point is the clothes he left his house in," Monte Schulz said. "Everything else is gone."