Officials say the flooding is the worst since Hurricane Irene.

The flash floods across New England, New York and Quebec on Monday evoked frequent comparisons to Hurricane Irene, which inundated the region in 2011 after making landfall and being downgraded to a tropical storm. Irene killed at least 40 people in 11 states and caused more than $6.5 billion in damage.

Gov. Phil Scott of Vermont said he feared that the sheer volume of water dumped on his state by this week’s storm system could surpass the amount that fell during Irene, because the region will be pummeled by rain for several days.

“What’s different for me is that Irene lasted about 24 hours,” he said at a news conference on Monday morning. “We’re getting just as much rain, if not more, and it’s going on for days. That’s my concern. It’s not just the initial damage.”

The Winooski River running through Vermont’s capital of Montpelier is expected to crest on Tuesday at its second-highest level ever, at 19.8 feet. That’s almost a foot higher than the river reached after Tropical Storm Irene in 2011. The record-high crest — of over 27 feet — occurred during Vermont’s “greatest natural disaster,” the floods of November 1927, according to the National Weather Service.

Over the past two weeks, many parts of central and northern New England have received 200 to 300 percent of their normal rainfall for the same time period, according to forecasters with the Weather Service’s Weather Prediction Center.

When Hurricane Irene moved north from the Caribbean in 2011, it brought with it fears of coastal flooding, which turned out to be relatively minor. Instead, the storm caused the most severe flood damage after it moved over the mountains of New England and New York, where the combination of steep, rocky terrain and raging rivers and streams led to disaster.

In Vermont, hundreds of miles from the ocean, Irene damaged hundreds of roads and bridges, turning picturesque villages into veritable islands surrounded by deep mucky water. At least half a dozen people were killed in Vermont.

In the mountain towns of upstate New York, houses were swept clean off their foundations by Irene, and one woman drowned inside a vacation cottage that became submerged in a rapidly rising creek. In the Catskills alone, rescuers saved almost 200 people from rising waters that surrounded their homes or motor vehicles, state and local officials said.