LEBANON — A heavy rainstorm that began Sunday night continued to batter the Upper Valley through Monday, as rivers swelled up with rainfall and snowmelt, hastened by temperatures in the low 60s. Power outages, closed roadways and early school dismissals abounded.

Schools in the Mountain Views, Windsor Southeast and White River Valley supervisory unions were among those who sent students home early as nearby streams swelled through the course of the morning.

“There have been a few times we’ve closed early for snowstorms, but it hasn’t been for flooding in awhile, and not in December,” said Kristy White, administrative assistant for the White River Valley Supervisory Union.

Rivers are expected to crest Tuesday morning. The Connecticut River in West Lebanon is forecasted to peak at 18 feet around 1 a.m., double its height at the same time early Monday, according to National Oceanic and Atmospheric Administration data.

Around 1 p.m. Monday, a United States Geological Survey stream gauge on the White River in West Hartford recorded water at 13 feet, having risen four feet in four hours. NOAA forecasted the river peaking at 15 feet around 6 p.m. the same day. Historic flooding in July brought the river over 18 feet.

“Rain’s still coming down and we’re looking at more to come,” said Jon Palmer, a meteorologist with the National Weather Service in Gray, Maine.

Just under an inch of rain had fallen by Monday, according to a National Weather Station gauge at the Lebanon Municipal Airport. Another inch is expected to fall overnight, Palmer said.

In Vermont, high waters closed Route 14 in Randolph between South Randolph Road and Kingsbury Road, and Route 106 in Perkinsville between Route 131 and Little Ascutney Road. A flurry of town roads across both states closed as well throughout Monday.

Elsewhere in Vermont, swift water rescue teams responded to calls in Ludlow, Chester, Waterbury and Berlin. In Jamaica, Vt., three people were rescued from a water-bound house.

As of 11 a.m., nearly 600 Barnard residents — 65% of Green Mountain Power customers in the town — were without power. By 3 p.m., power had been restored there. Other high impact areas on the Vermont side of the Upper Valley included Strafford, Newbury and Windsor, where 50 residents remained without electricity into the afternoon.

Outages were far more extensive in New Hampshire Upper Valley towns, where thousands of residents were without power, according to utility outage maps. As of 11:45 a.m. on Monday, the lights were off for all or nearly all of New Hampshire Electric Co-op customers in Claremont, Orange, Plainfield, Cornish, Haverhill, and three-quarters of Grafton. Half of the Eversource customers in Haverhill and Grantham were without power.

In Unity, rain and snowmelt had rendered several roads “mud season impassable,” and power was out for a few hours in the town office, said Garry Bator, chairman of the Selectboard.

Early Monday morning on Church Road, a branch that had fallen onto a pair of power lines burst into flames as electricity zapped through the wires, said Unity Fire Department Chief Tim Davis. But when the power cut out, the situation resolved itself, despite response from Davis’ department.

“There was no more electricity running through the branch,” he said. “It just went out on its own.”

In Tunbridge, Road Foreman Rodney Hoyt kept his crew in the garage. Hoyt’s holding his trucks back so that they don’t dig up the town’s now soft dirt roads. “I can only make a bigger mess by getting out there and trying to do something,” he said. Around 11 a.m., he noted that the White River had already spilled over the Tunbridge Fairgrounds.

But he’s hoping the rain “draws some of the slime off the top of the road,” he said. “I know it’s hard to believe, but an old-timer will tell you that rain will make mud better.”

No matter the outcome, the road crew will “certainly have work to do” once the weather passes, Hoyt said.

As the weather dries out on Tuesday, temperatures are expected to steadily drop and once again dip below freezing at night.

But on Monday, moisture content, known as the “dew point,” registered throughout the day on the gauge at the Lebanon airport spelled the end of much of the area’s snowpack.

Around 2 p.m., the dew point registered at the Lebanon Municipal Airport was 58 degrees, as temperatures hovered around 63 degrees. The higher a dew point is above freezing, the faster the air eats up snow, said Palmer, the meteorologist.

At Whaleback Mountain, an Enfield ski area, Executive Director Jon Hunt looked out the window as snow “was quickly going down the river,” he said.

Man-made powder, which the mountain had started producing within the last couple weeks, is no magic bullet. It still must contend with spurts of warm weather and rain. As of Monday, most of it had either turned brown or disappeared.

When snow is wiped out, “it definitely hurts the bottom line a bit,” Hunt said. “But we feel optimistic about being able to catch back up.”

The mountain is still scheduled to open for skiing the week after Christmas.

Frances Mize is a Report for America corps member. She can be reached at fmize@vnews.com or 603-727-3242.