(Wikimedia Commons)

Firefighters in the Glendora area predict that the valley and foothills could receive as much as four inches. And so much rain in such a short period of time could cause traffic congestion, accidents and mudslides.

The hills above Glendora are especially vulnerable to landslides due to the effect of heavy rain on areas recently burned by the Colby Fire in January.

Fire stations are supplying sandbags to place around houses, and residents of the foothills are putting concrete barriers around roads to keep out falling rocks.

Even in the city, the rain still poses a risk since it could cause more accidents as it mixes with oil built up on street surfaces, making roads more slippery.

The rain is not predicted to hit downtown Los Angeles so hard, but it is expected to get 3.6 inches, at least half of the rainfall that fell in all of 2013. 

Firefighters are also concerned that the storm sewers could get overwhelmed and cause flooding, since they have been out of use for so long.

Glendora fire stations could not be reached for comment.

Reach Executive Producer Anne Artley here