Florida ? Lake Okeechobee was expected to drop this week to its lowest level on record, threatening a key source of water for nearly 5 million people and the Everglades during South Florida’s worst known drought.

The nation’s second-largest freshwater lake held at 9 feet on Tuesday, less than a half-inch above the previous record of 8.97 feet, set May 24, 2001, after another long drought. The average water level for this time of year should be around 13 feet.

The 18-month drought already has led to severe water restrictions for homes and businesses across the state. Limits have been placed on watering lawns and washing cars. Citrus growers and other farmers also have had to cut their water use by half.