(CBS/AP) A four-day deluge has turned streets into rivers across New England, flooding homes up to their door knobs, forcing dozens of schools to close because the buses couldn't get through, and threatening dams and communities as rivers rise.

The rain totals could hit 15 inches by afternoon, triggering the worst flooding in some areas since 1936, the National Weather Service said.

"Yesterday, 3.77 inches of rain fell in Boston, shattering an old record, so that just gives you an idea of how heavy the rain has been," says CBS News Meteorologist George Cullen, adding that showers could last into Wednesday.

Hundreds of people were ordered to leave their homes. Dozens of businesses and offices were closed.

The Merrimack River, which chased more than 100 people from homes in Manchester, N.H., was more than eight feet over flood stage early Monday and rising, and the Charles and other large rivers could swamp entire neighborhoods if they spill their banks.

Further downriver, in Haverhill, Mass., CBS News' Cheryl Casone reports the flooding was made worse by a break in a sewage line.

"The mix is 90 percent storm water, 10 percent sewage, right now
about 50 million gallons per day" was ending up in the overflowing Merrimac River, said Haverhill Sewage Treatment Plant acting director Bob Ward

Just north of Massachusetts, fast-rising floodwater forced scores of families to flee homes near the Mousam River in Maine.

Four-wheel drives have been used to get people out of their homes in Peabody, Mass., reports Carl Stevens of CBS Radio station WBZ-AM. Much of the downtown area is underwater.

"Because residents of Peabody are used to flooding and because they could see this coming, they were able to get out in time," reports Stevens. "But residents who've lived in this city for decades say while they've seen flooding, they've never seen it this bad."

"When you get 12 inches of rain in two or three days, I'm not sure that you can prepare for that," Peabody police chief Robert Champagne told CBS Radio News. "I've been in this business for over 30 years and been the police chief for almost 20, and this is the worst sort of flooding we've seen in a long time."

"This is unbelievable," resident Wayne Brooks said on CBS News' The Early Show. "Everything that was downstairs is under water."

"This is the tip of the iceberg. It's going to get worse," Massachusetts Emergency Management Agency spokesman Peter Judge said Sunday. "We fear that 15 rivers will be pushed over flood level or right up to flood level."

The governors of New Hampshire and Massachusetts declared states of emergency, while Maine Gov. John Baldacci declared a state of emergency for his state's southernmost county, York County.

"When the water goes down, we'll start cleaning up. Get a big dumpster and just start throwing stuff away. And we'll start again," said Brooks, who two months ago was "downsized" and lost his job.

Several roads, including portions of busy Route 1 north of Boston, were closed Monday because of flooding, and many school systems in the region canceled classes.

At least one telephone central office in New Hampshire was flooded, causing problems with calls.