The second storm, forecasters say, could bring thunder and dump up to 2 inches of rain in central and southern valleys, 2 to 4 inches in the foothills and up to 6 inches in some mountain spots.
State water officials plan Thursday to survey the anemic mountain snow pack, and will likely find that California's precipitation is badly lagging what's needed to quench the region's thirst. 2013 was California's driest year on record.
In Nevada, the first of back-to-back storms dropped several inches of snow at Lake Tahoe and up to a foot and one-half on the mountain ridges.
A winter weather advisory was put into effect from 4 p.m. Wednesday to 10 a.m. Thursday for the Reno-Tahoe area, south to Mammoth Lakes.
The second wave of wetter weather begins Friday night into Saturday.
Triple digit heat has many people staying cool inside. But outdoor workers don't have that option.
Highway 140 will reopen Thursday afternoon after a mudslide made the road impassable in Yosemite National Park.
The "well above-average" rain of the past three months in California has not brought any improvement to drought conditions in the state.
The National Weather Service in Reno is warning of flash flooding in the Reno and Truckee areas until 5:15 p.m. The weather service is reporting severe thunderstorms and hail.
The National Weather Service is forecasting thunderstorms for the Sierra starting Tuesday through Thursday.