Authorities have lifted an evacuation order for nearly 200,000 California residents who live below the crippled Oroville Dam that threatened to collapse and cause catastrophic flooding.
But Butte County Sheriff Kory Honea warned on Tuesday that residents should stay prepared in case the situation changes.
He said the water level at the lake behind Oroville Dam, the US's tallest dam, is now low enough to cope with a storm that is due over the next few days.
The National Weather Service's Sacramento office said heavy rain will fall in the area on Wednesday and Thursday morning, with two to four inches in the foothills and mountains.
But the storm is looking colder than first thought, meaning lower snow levels and less run-off into Sierra reservoirs than the storms last week.
The Latest: Nearly 200,000 dam evacuees in California allowed to go home. https://t.co/ssSfrz6WZa— The Associated Press (@AP) February 14, 2017
Crews have been working around the clock to repair the dam's damaged spillway.
A California dam inspector said authorities may never know the exact cause of the earth and concrete blow-outs below the dam.
Eric Holland, of the state Department of Water Resources' dam-safety division, said any of a number of different problems could have caused the spillway troubles. Holland said authorities often never discover in these cases what exactly happened, because flood water has washed out everything at the scene.
Authorities ordered mass evacuations on Sunday for everyone living below the lake out of concern that the spillway could fail and send a 30ft wall of water downstream.
White House spokesman Sean Spicer said President Donald Trump is keeping a "close eye" on the public safety crisis caused by the damaged dam.