Mr. Levitt, who lives in Manhattan, learned the hard way that if he sits outside for an hour or more, his feet turn into blocks of ice. He likes to wear warm shoes with a few layers of socks, and he, his wife and children also bring blankets.

With their hats, winter jackets and gloves, outdoor guests look like winter sports enthusiasts. Erika Chou, a Manhattan restaurateur who runs the Kimika and Wayla spots, saw people come in “head to toe in full snowboarding outfits like Burton,” she said.

Mr. Li swears by fleece-lined Heattech pants from Uniqlo and thick wool socks from LL Bean. Ms. Siskin has “a few tricks I’ve learned,” she said, including long underwear under her jeans and a thin Patagonia liner under her coat.

One final evening, “I went to dinner and wore the air-activated foot warmers that you buy for skiing,” she said. “I also got this hand warmer that changed the game,” a rechargeable model from Ocoopa.

Restaurant owners also help their customers stay warm. The Odeon in New York’s TriBeCa neighborhood has ubiquitous infrared heat lamps and microfiber blankets that can be rented for $ 7 or bought for $ 20. The restaurant also has mylar blankets such as those made available to marathon runners for customers to use for free. Many other restaurants also offer blankets that they wash or dry clean after each use.

Even the best dishes don’t taste that good cold, so it’s worth considering how a restaurant has adapted.

In the fall, Cédric Vongerichten, the chef and owner of Wayan, which serves Indonesian food with a French flair, found that dishes like lobster noodles went cold in minutes. Inspired by his childhood in France, Mr. Vongerichten introduced a burner device like the one for cheese fondue that plugs into a socket at selected tables, a concept he calls Indo-Chalet.