ATLANTA, Oct. 15 — For the first time in more than 100 years, much of the Southeast has reached the most severe category of drought, climatologists said Monday, creating an emergency so serious that some cities are just months away from running out of water.

In North Carolina, Gov. Michael F. Easley asked residents Monday to stop using water for any purpose “not essential to public health and safety.” He warned that he would soon have to declare a state of emergency if voluntary efforts fell short.

“Now I don’t want to have to use these powers,” Mr. Easley told a meeting of mayors and other city officials. “As leaders of your communities, you know what works best at the local level. I am asking for your help.”

Officials in the central North Carolina town of Siler City estimate that without rain, they are 80 days from draining the Lower Rocky River Reservoir, which supplies water for the town’s 8,200 people.