The rain will continue off and on through Saturday in most parts of the county with a brief respite Wednesday, the San Diego office of the National Weather Service said.

"This system is expected to be quite cold aloft which increases the chances of thunderstorms across the area, leading to an increased threat of flooding."

Volunteers are working to rebuild homes damaged by last year's floods, while the City of San Diego is preparing for potential flooding by conducting maintenance on storm drains and street sweeps.

Schools in the Spencer Valley School District closed at noon Thursday due to inclement weather and hazardous road conditions.