The heavy rain caused mud and debris to overflow Mill Creek at Forest Falls in the San Bernardino National Forest. The National Weather Service said the creek swelled to about 100 feet in some places.
"A little bit of rocks, a lot of trash, a little bit of lumber and a lot of dirty water," said Jon Knapp, visiting from Yucaipa. "I think it came up five feet within a minute."
The water also washed over some roads and came close to a bridge on Forest Falls Highway.
Many areas got several inches of rain in less than an hour.