More of the nation is in the grip of drought than at any time in the past 12 years, including over half of the contiguous United States, according to the U.S. Drought Monitor.

The National Drought Mitigation Center at the University of Nebraska-Lincoln, established in 1995, says 46.8 percent of the nation’s land area is in moderate drought, or worse, a record for the Drought Monitor’s 12-year existence.

For the 48 contiguous states, the figure rises to 55.9 percent. Large parts of California were shown in moderate to severe drought, with much of Orange County listed as “abnormally dry.”

Widespread heat and dryness are to blame, the agency says.

“It started, really, last fall, and it lasted over the winter and spring,” said Mitigation Center Director Michael J. Hayes. “It was very warm and dry for a large part of the country. I think all that, combined with the recent dryness and heat, caused this outbreak of moderate drought to occur.”

Much of California has been dry, with water content in the state’s snow pack at only 40 percent of normal.

Reservoir storage, however, remains above normal because of wet conditions last year, according to the California Department of Water Resources.

In coastal Southern California, wildfire risk is considered above normal for mountains and foothills, an assessment from the U.S. Forest Service’s Predictive Services group shows.

Despite some rain the spring, “we’ve had enough of a period now that our fuel is starting to dry out,” said meteorologist Cynthia Palmer of the National Weather Service. “We’re dry.”

John Wayne Airport has seen 3.87 inches of rain since Jan. 1, more than five inches below normal for the period.

This year the U.S. also saw its warmest spring on record.

Although it might be tempting to link the drought conditions with long-term climate change, Hayes said it’s too soon to draw such a parallel.

“Heat waves and drought events are normal parts of the climate in the U.S.,” he said. “We’ve always had them, we have them this year, we’ll continue to have them in the future. Connecting this to anything long term is probably something that, later on, people are going to have to go back and assess, and see how it fits into long-term trends.”

Other scientists said this week that while no single drought or heat wave can be linked directly to climate change, they see signs of extreme events growing more frequent and more intense.