Volunteers searching for human remains in the wake of the wildfire that destroyed the California city of Paradise were delayed in their work on Friday, when a downpour turned ash from the fire into a thick paste, making it more difficult to find fragments of bone.

Craig Covey, who leads a search team from southern California’s Orange county, said those looking through the devastation in Paradise and two nearby communities were not told to stop but that he chose to take a break until the rain cleared. Heavy rain and strong winds were knocking over trees, raising the risk they could fall on searchers, he said.

“It’s just not worth it. We’re not saving lives right now, we’re recovering lives,” Covey said.

The deadliest US wildfire in the past 100 years has killed at least 84 people and more than 560 are still unaccounted for. Despite the inclement weather, more than 800 volunteers searched for remains on Thanksgiving and again on Friday, two weeks after flames swept through the Sierra Nevada foothills, authorities said.

Covey’s team of about 30 had been working for several hours on Friday morning before stopping and returning to a staging area with hot coffee and food under two blue tents. An electric heater provided warmth. While the rain was making everybody colder and wetter they were keeping the mission in mind, volunteer Chris Stevens said, standing under an awning as the team waited out a stretch of heavy rain.

“Everyone here is super committed to helping the folks here,” he said.

Searchers take cover from the rain in Paradise, California, on Friday. Photograph: Kathleen Ronayne/AP

Two days of showers have complicated the search but also helped nearly extinguish the blaze, said Josh Bischof, operations chief for the California department of forestry and fire protection (Cal Fire), adding that once the rain clears, state officials will be able to determine if the blaze is fully out.

The Camp fire ignited on 8 November and destroyed nearly 19,000 buildings, most of them homes. That is more than the worst eight fires in California history combined, Cal Fire said, with thousands of people displaced.

Volunteers interrupted by rain Friday found other ways to help. Covey and several team members took two big brown bags of lunch to 64-year-old Stewart Nugent, who stayed in his home and fought off flames with a garden hose, a sprinkler and a shovel. He’s been there for two weeks with his cat, Larry.

The first winter storm to hit California has dropped 2in to 4in of rain over the burn area since it began Wednesday, said Craig Shoemaker with the National Weather Service (NWS) in Sacramento. The NWS issued a warning for possible flash flooding and debris flows from areas scarred by major fires in northern California, including the areas burned in Paradise.

Shoemaker said the rain had been steady, but forecasters expected the heaviest showers in the afternoon.

“So far we’ve been seeing about a quarter-inch of rain falling per hour,” he said. “We need to see an inch of rain per hour before it could cause problems.”

He said the rain was expected to subside by midnight, followed by light showers Saturday.