Persistent rain over the last month has set the stage for the dangerous flood conditions that are expected to continue across parts of New Hampshire and Vermont. The deluge has so far wiped out roads, taken down bridges and forced the evacuation of a mobile home park.

Rain storms that have moved across the region “almost every day for the past month,” saturated the soils in the Twin States, said Jon Palmer, a meteorologist with the National Weather Service in Gray, Maine.

“This is a large system, and the ground just can’t take any more water at this point,” Palmer said. “All the water is running off and into the streams, and just kind of piling there.”

Localized concentrations of heavy rain have exacerbated flooding.

“This storm pivoted around an axis that ultimately just put Vermont right in the center,” he said.

At the West Hartford monitoring station on the White River, operated by the National Oceanic and Atmospheric Administration, water levels are expected to crest around 7 p.m. at 20.4 feet, which is half a foot below major flood stage.

At 19 feet — which the river is supposed to reach by early evening — the National Weather Service predicts widespread flooding of fields and lowlands throughout the valley, and waters will approach homes and businesses near the river.

At the West Lebanon monitoring station run by the National Oceanic and Atmospheric Administration, the Connecticut River is forecasted to crest at 23 feet around midnight. That would be the highest the Connecticut River has gotten since Tropical Storm Irene in August 2011, when the river crested at just shy of 30 feet in West Lebanon.

The Connecticut River in Lebanon and West Lebanon is expected to surpass minor flood stage overnight on Monday, and crest back down by Tuesday morning, Palmer said.

As climate change drives temperatures up, warmer atmospheric conditions hold more water vapor. As a result, New England has experienced the largest increase in extreme precipitation events over the past quarter-c entury than anywhere else in the country, according to a study from Dartmouth scientists published in  May.

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