Derril Shiflet, who was visiting from Arizona, didn't bother to unpack his bags in case he needed to evacuate his sister's home quickly.
"It's been hectic, people in the backyard all day, and we don't know if the mud is coming down. It's been pretty bad," Shiflet said.
Cal Fire firefighters and inmate crews were back at it on Wednesday morning, shoring up the hills and sandbagging neighborhood streets.
"The workers have done an incredible job. They've been working night and day to make sure the hillside's secure, and them doing that makes me feel safe," said Ross Horner of Highland.
Rescue crews are on standby in case of a slide.
"Everything that they have done here is amazing. They're saving the houses, everything is draining the way it's supposed to be, I mean, the resources that have been brought in, we can't thank them enough," said Kimberly Mays of Highland.
In nearby Loma Linda, the California Conservation Corps helped residents shovel mud after a hillside gave way.
More than 700 residents volunteered to help with rain preparation on Tuesday. More than 100,000 sandbags are in place around Highland.
Bill Peters of San Bernardino Cal Fire said they are more prepared than a week ago when the mud started flowing.
"With all the sandbags and the K-rails that we have laid over the last week creating our diversion channels and our walls, we're being very proactive, and we're ahead of the game," Peters said. "We've done as much as we can getting prepared for this. We think we're in pretty good shape, and honestly if the rain stays like this, we feel pretty positive we're going to weather it."