PARIS — It was a chilly winter afternoon on Rue Montorgueil, a cobbled pedestrianized street in central Paris lined with dozens of outdoor cafe terraces. The temperature barely exceeded 50 degrees Fahrenheit, and the sun was hiding behind large fluffy clouds.

Yet despite the crisp weather, Pierre-Louis Le Tolguenec was sipping his beer on a terrace, wearing a T-shirt and no jacket as if it were summer.

The reason for this paradox hung over his head: orange lamps throwing out heat, creating a microclimate.

“It’s a French cultural habit to be on a terrace in summer as well as in winter,” said Mr. Le Tolguenec, a 25-year-old engineer — although he acknowledged, “in this case it’s a little bit too much.”