A nor’easter fueled by the remnants of Hurricane Willa is set to slam the Big Apple this weekend — causing gusts up to 50 mph, severe flooding and heavy rainfall across the region.

Willa, originally a Category 5 hurricane, rocked west-central Mexico this week before weakening into a tropical storm. Some of the leftover moisture from the storm is expected to make its way from the Deep South into the Northeast, according to AccuWeather.

“Even if there wasn’t the remains of Willa, there would be a strong storm system,” said AccuWeather senior meteorologist Tom Kines. “The moisture is helping to contribute to the storm.”

The rain was expected to move in just after midnight Saturday morning, with the heaviest downpour expected between 3 a.m. and 3 p.m. Most of the region can ­expect one to two inches of rain — ­although three are possible.

“Anybody is fair game for heavy rain,” Kines said.

Temperatures Saturday rise from the 40s into the mid-50s, according to predictions. Wind gusts will approach 50 mph, and 35 to 40 mph inland.

A flash-food watch will be in effect in the five boroughs, as well as parts of Long Island, New Jersey and Connecticut through Saturday afternoon. Coastal flood warnings were issued in “vulnerable coastal locales” along Jamaica Bay and the western part of Long Island Sound.