MONTPELIER, Vt. — Heavy rains and melting snow and ice pushed rivers toward or above flood stage around Vermont, New Hampshire and Maine on Tuesday with the city of Montpelier warning residents to expect some street and basement flooding by early Wednesday.

The National Weather Service issued flood watches for most of the three states and portions of upstate New York while flood warnings — meaning flooding is taking place or imminent — were issued for some areas.

In flood-prone Montpelier, city officials urged downtown residents and business owners to prepare for overnight flooding.

“We’re expecting that there will be some flooding. We’re not expecting it to be super dangerous,” said City Manager William Fraser.

The city’s emergency operations center was scheduled to open at 7 p.m. Tuesday to monitor the conditions and officials closed a low-lying parking lot off State Street, near the confluence of the Winooski River and its North Branch.

The Winooski River was projected to hit flood stage level between 8 p.m. and 10 p.m., cresting at 16 feet between 1 a.m. or 2 a.m., and then start to recede, Fraser said.

Cold temperatures could make some parts of the city slick, he said.

The National Weather Service expanded flood areas throughout the day Tuesday as the heavy rains moved in. The flood warning zone grew to include Addison County, and portions of Washington, Rutland and Lamoille counties in Vermont. Earlier warnings had been issued for the Otter Creek at Center Rutland, the Lamoille River at Johnson and Jeffersonville, Barton River in Coventry and along the Connecticut River near Wells River and West Lebanon, N.H., and for the portion of the river near Lunenburg, Vt., and Dalton, N.H.

In Maine, the National Weather Service in Caribou said it was keeping an eye on reports of ice jams in the St. John River that runs along the Canadian border. Northern and eastern Maine are anticipated to get between 1 and 1.5 inches of rain Tuesday through Wednesday, increasing the risk of flooding than can be caused by ice jams.