Frustrated rescue workers and volunteers on Tuesday spent a second day searching miles of rugged woods, hills and ponds for a 3-year-old boy who wandered away from home.

The best clue so far in the search for Joshua Childers came Monday evening when a searcher found one of his shoes nearly a mile from the family's mobile home, which sits along rough, rural terrain in the Mark Twain National Forest about 100 miles southwest of St. Louis.

The weather was turning worse as nightfall approached Tuesday, with a chance of heavy rain overnight. Police pulled in many of the volunteers but sent out every available search dog. Police helicopters circled the area and the Missouri State Water Patrol had searched three ponds with divers and dragging by Tuesday evening.

Madison County Sheriff David Lewis remained confident the 35-pound boy was still alive.

"I don't know why he wouldn't be," Lewis said Tuesday. "It wasn't that cold last night."

Joshua wandered away about 11:30 a.m. Monday from his home near Arcadia, wearing a dark blue and green T-shirt, pull-up diaper and tennis shoes. His mother had been watching him but was briefly distracted, authorities said.

Police were called 45 minutes after the boy disappeared. Hundreds of volunteers showed up to help in the search, but by Tuesday afternoon they were mostly watching and waiting because so many professional emergency workers were assisting.

Lewis said it would be easy for a small boy to get lost in those woods.

"You can't see 20 yards in front of you there," he said. "This is very rugged terrain, very rough, with thick underbrush."

Volunteers showed up on horses, on donkeys, on all-terrain vehicles or with their own dogs to help.

"It hits pretty close to home," said Randy Johnson, 31, of nearby Bismarck, a corrections officer at a prison. "When I heard about it I told my wife I had to come down here and do something."

Lewis decided to send volunteers out only in small groups, in part to keep them from getting lost or hurt, and partly to make sure he kept people fresh in case the search dragged on for days.

Lewis said the boy's father was among those searching the woods. The mother was waiting at home, in case Joshua returned.

Asked how they're holding up, the sheriff said, "They look a little dazed, actually."