PHILADELPHIA -- Balmy temperatures that brought a spring-like feel to the eastern United States on Monday belong to a treacherous dry-weather pattern blamed for worsening drought conditions from Maine to Georgia, Reuters quoted meteorologists as saying.

As commuters in New York City and Philadelphia traded heavy winter coats for spring jackets, Pennsylvania environmental officials warned of possible mandatory water restrictions for cities such as Harisburg, York and Allentown to combat the worst drought in three years.

New York mayor Michael Bloomberg has asked residents of America's leading metropolis to curtail water consumption as supplies dwindle to their lowest levels in more than 30 years.

The city of Baltimore, plagued by reservoir levels at only 61 percent of capacity -- the lowest ever for late January -- was due to begin pumping drinking water from the Susquehanna river this week for the first time since the drought of 1999, which was the worst since the Great Depression.

And in Maine, where 2001 proved to be the driest in 107 years of record-keeping, state authorities warned that as many as 2,000 private wells have run dry, while lakes in the north and east stand at a mere 29 percent of capacity.

"The drought is worsening," said David Hess, secretary of the Pennsylvania Department of Environmental Protection. "We are seeing a continual decline in ground water levels and stream levels at a time when they should be going up."

Citing a 6 inch to 13 inch (15 cm to 33 cm) precipitation deficit, Hess said a drought emergency could be imposed on cities of south-central and southeastern Pennsylvania within weeks unless precipitation levels rise to well above normal.

That would force water systems to cut back on usage by 15 percent, require industrial plants to draw up formal water conservation plans and ban all use deemed "nonessential."

"The last time we were in a drought as deep was in '99, and it took two hurricanes to get us out," Hess said.

Meteorologists say rainy coast has suffered mainly from the recurrence of high-pressure systems that have kept the jet stream contained well above the Canadian border and deflected moisture from the Gulf of Mexico.

Scientists say the phenomenon, known as a positive North Atlantic oscillation, has become more frequent in recent decades with a rise in average temperatures that many associate with global warming.

Eastern communities also saw little last year in the way of autumnal downpours from hurricanes and tropical storms that normally replenish reservoirs and aquifers.

Drought conditions pose a special problem in the winter, when water supplies are usually recharged by a combination of precipitation and slack water consumption.

"Strains are now starting to show on municipal water supplies," said Mark Svoboda, a meteorologist with the National Drought Mitigation Center at the University of Nebraska.

Weather experts said the severity of the drought could now depend on how much rain the region receives in the spring. On Monday, the National Oceanic and Atmospheric Administration said drought conditions were possible for early spring.

But with an El Nino weather pattern expected to form in the southern pacific later this year, meteorologists said the outlook for precipitation was unclear.

Douglas Lecomte, senior meteorologist at NOAA's Climate Prediction Center, said there was only a 50 percent chance of a wet spring. But he expressed optimism that drought conditions could begin to ease soon. "We really don't see any reason for the abnormal dryness to continue," he said.