Doyle Rice

USA TODAY

So far, California is enduring its hottest year on record, contributing to the state's worst level of drought in the past 40 years, according to a report from the National Climatic Data Center released Thursday morning.

Through the first five months of the year, "temperatures in California have been about 5 degrees above average," said Jake Crouch, a climate scientist with the center in a conference call with reporters.

The warmth in California has contributed to the drought that's now encompassing the entire state, according to the weekly U.S. Drought Monitor released Thursday.

Nearly one-third of the state is now in "exceptional" drought, the worst level, the monitor reported. This is the highest percentage in the history of the Drought Monitor, which began in 2000. Exceptional drought is now seen in the San Francisco Bay area, parts of Silicon Valley and the farmlands of central California.

"From northern portions of the Coastal Range to Mt. Shasta, precipitation since October 1 totaled 30 to 50 percent of normal," wrote Eric Luebehusen of the U.S. Department of Agriculture in the monitor. Deficits of 16 to 32 inches of rain were reported.

The drought is now comparable to the state's drought in the 1970s, according to Crouch. Drought impacts are likely to eventually be much higher than 40 years ago, however: While about 20 million people lived in California in the 1970s, the state's population is now nearly 40 million.

A report last month from the University of California-Davis "estimated that water shortages would cause the fallowing of 410,000 acres, the loss of 14,500 jobs and cost the (agricultural) industry $1.7 billion in the state's most productive agricultural region."

Looking ahead, ongoing dry and warm conditions are forecast in the West for the next three months, said Steve Baxter, a meteorologist with Climate Prediction Center at the National Oceanic and Atmospheric Administration (NOAA)..

Beyond that, "we're still expecting El Niño to develop later in the summer and continue into the fall and winter," Baxter said. El Niño is a warming of tropical Pacific Ocean surface water that impacts weather around the world. He said there's an 82% chance it will develop by the fall and winter.

Baxter said it will likely be a weak to moderate El Niño, but there's a still a chance it could be a strong one. El Niños often, but not always, bring needed rain and snow to the West, including California.

For the spring season, which climatologists define as March, April and May, California had its 5th-warmest spring on record, while both Wisconsin and Louisiana had their 11th-coldest spring.

As for spring precipitation, Crouch said that Washington state had its fourth-wettest spring on record, and Kansas had its third driest.

Global climate numbers for May, spring and the year-to-date will be released by NOAA on Monday.