October, said the calendar. Before Halloween. And the 2.5 million trees occupying New York City’s open spaces confirmed it was fall — not winter — with glorious canopies of leaves stretching along their boughs.

Yet snow was falling. Not a light, mischievous form of frozen precipitation, either, but heavy, wet flakes driven on the gusts of an angry weather system barreling across the Northeast from the Atlantic Ocean on Saturday, cracking sturdy limbs and toppling power lines as it went. It also shattered records, threatening some more than a century old, and elicited the kinds of warnings from public officials that are not usually heard until deep in winter.

On Sunday,about 2.3 million customers from Pennsylvania reaching up into New England found themselves without electricity, according to reports, as the region was lashed by surprisingly high winds, snowdrifts and surging seas. On a weekend that might normally have been spent raking leaves, people were forced to react quickly — retrieving shovels, charging batteries, finding fuel for generators, searching for boots and mittens and checking refrigerators and cupboards.

In Connecticut, Gov. Dannel P. Malloy said at a briefing Sunday morning that more that the 750,000 homes were without power, breaking a record for the state that was set in August when the remnants of Hurricane Irene hit the state. People could be expect to be without electricity for as long as a week, the governor said.