Santa Ana winds will continue whipping through Southern California through Thursday, sparking fears that progress made fighting wildfires that have scorched over 40,000 acres and left 28 dead could be reversed and more blazes could break out.

Much-needed rain has begun to fall over Southern California, bringing relief to the drought-stricken region but also the threat of toxic runoff.

More rain fell Monday on parts of Southern California after causing mudflows over the weekend, helping firefighters but boosting the risk of toxic ash runoff in areas scorched by Los Angeles-area wildfires.

The first significant storm of the season brought snow and downpours to Southern California that doused wildfires and caused some ash and mud to flow across streets in the Los Angeles area on Monday.