Crews searched overnight for an 8-year-old autistic boy who disappeared Monday morning in the San Bernardino National Forest.
Temperatures were in the low-60s Monday night, but rain was falling early Tuesday in the area.
"We're concerned about the current weather," said Sgt. Bryan Lane. "The rain is going to change certain aspects of the search today."
The terrain was described as rugged and steep with loose rocks.
Lane said about 30 search team members would be on the ground Tuesday. Aerial and canine units also will join the search for Joshua Robb, who was wearing shorts, a t-shirt and sandals when he ran away from school Monday morning.
"He was able to squeeze between the fence and escape into the forest, we believe," said Lt. Rick Els of the San Bernardino County Sheriff's Department.
Robb was seen running from Grandview Elementary School in Twin Peaks. Staff members chased the child, but could not catch him before he ran into the forest, said San Bernardino County sheriff's spokeswoman Cindy Bachman.
His father, Ron Robb, said the boy had been taken into protective custody last month, and he strongly suspects he ran away from school to find his parents.
"He's always been a flight risk," said Robb.
Robb said the family was forced out of their home last month by a foreclosure proceeding. He said a realtor called government officials after noticing that the boy had been restrained.
"We had to lightly tether him while we were moving stuff out of our house," said Robb. "We know for a fact that the reason he escaped was because he was trying to look for mom and dad."
The boy was described as an autistic white male, four and one-half feet tall, 60-75 pounds with brown hair.
School officials notified sheriff's at the Twin Peaks station about the missing boy as soon as they discovered he was gone, which launched a search involving deputies, citizen volunteers, and California Highway Patrol officers.