Across industries, California businesses are monitoring weather, rainfall, rising river levels — and especially burned areas that are barren and susceptible to mudslides with excessive rainfall.
"Where we have the biggest concern is the burn areas," said Cheri Hummel, vice president of emergency management and facilities for the California Hospital Association. The trade group represents about 400 hospitals in the state.
And while regional hospitals have been preparing for El Nino for months, California often seems to have its share of natural disasters, including earthquakes, wildfires, floods and droughts. Disaster preparedness efforts for hospitals include ensuring emergency backup supplies of power, fuel and water.
"A few months ago it was drought, and now we're preparing for El Nino," said Jan Emerson-Shea, a spokeswoman for the hospital association. "It's feast or famine."
Down in the Central Valley, in the middle of California, farmers are also tidying agricultural properties in advance of severe weather. Farmers are doing things like ensuring drains and creeks are cleaned and open.
Read MoreCalifornia farmers shore up for El Nino
For agricultural regions, a big concern is four consecutive years of a drought that have created extremely parched land. When land is that dry, vast amounts of furious rainfall can only be absorbed at a certain pace with the remaining water leaving the land quickly susceptible to mudslides and cascading land.
"The land has been so dry for so long, it's almost impermeable," said Mary Simms, a spokeswoman for the Federal Emergency Management Agency or FEMA. And like burned land, fallowed farm acres left to idle amid lack of water raises flash flooding concerns, Simms said.
The California drought in 2015 alone was forecast to result in the fallowing of 542,000 irrigated acres, according to an update last year from the University of California at Davis. Nearly all of that fallowed land was in the Central Valley.