Lakes and reservoirs in the southeastern United States are shriveling, and local governments are calling for sweeping restrictions to conserve what little water they have left. More than 25 percent of the region is suffering from “exceptional” drought, the National Oceanic and Atmospheric Administration’s most severe classification.

Kentucky, Virginia, Tennessee and Alabama are baking under exceptional or extreme droughts. Mississippi, Georgia and Florida are also suffering from severe drought, moderate drought or abnormally dry conditions.

The conditions are the worst in more than 100 years in many areas, and some cities, including Atlanta, Georgia, could run out of water in as little as 90 days. Siler City, North Carolina, has ordered water use cut in half.

State and local leaders are conserving water and considering sharing water between full water systems and those that are drying up. They are also imposing restrictions on outdoor and even indoor water use. Households, restaurants, businesses and industries are being ordered to sharply curtail water use.

If voluntary measures don’t work, some leaders have indicated that declaring a state of emergency and imposing mandatory rationing will be their only choice.

Worst-case scenarios forecast severe water shortages that will affect more than 4 million people.

The dry conditions are breeding wildfires, with North Carolina suffering from 5,964 of them so far this year, 2,000 more than usual. Over 33,000 acres have burned, twice the average.

“We’ve run after fires hot and hard all during the summer, and it’s not going to go away for the rest of the year,” state forester Dan Brandon said. “It’s an extraordinary situation. I’ve never seen it like this before.”

For more on national and global weather trends and what is causing them, read “Flash Floods, Scorched Earth.”