CENTER CONWAY, N.H. — The Saco River flows lazily here, from New Hampshire into Maine, ridged with sandy banks and lush forests, luring eager families in canoes and rowdy flotillas of young adults.

But after a hot, dry summer, a 10-mile canoe trip to Fryeburg, Me., from Center Conway, N.H., this month was interrupted, time and again, by the scrape of boat on sandy riverbed, and the grudging acceptance that the only way to get the canoe across certain stretches of shallow river would be to drag it.

The low river is one of countless signs of dry weather that has settled over much of New England. Conditions are even worse south of the Saco, with the United States Drought Monitor observing “extreme drought” conditions in much of the eastern half of Massachusetts, southeastern New Hampshire and the southern part of Maine.

Some private wells have dried up. Farmers face millions of dollars in lost crops, and federal agricultural officials have declared much of New Hampshire, Massachusetts and Connecticut a natural disaster area. Parts of rivers have withered into a series of ponds or wide stretches of stone, harming the ecosystems that depend on them. Bears and other wild animals are venturing into human habitats in search of food because there is little in their own.