WELLFLEET, Mass. — For as long as anyone knows, young sea turtles have ventured up the East Coast, leaving warm seas to feed on crabs and other prey. And some of them have lingered too long in northern waters and been stunned when the season turns cold.

Around this time of year, volunteers regularly patrol the beaches of Cape Cod Bay to rescue turtles that wash up at high tide — six of seven species of sea turtles are endangered — so they can be rehabilitated and relocated to warmer shores in the South.

But this year the usual trickle of stranded turtles has turned into a flood, and nobody seems to know why.

Since mid-November, volunteers on turtle patrol have found nearly 1,200, almost all young Kemp’s ridley turtles, the most endangered of turtle species. That is almost three times as many as in the previous record year, and many more times the number in an average year. More turtles are being found every day.