Café terraces are usually populated in the summer months here in Paris, when you can take advantage of the (occasional) nice weather.
But just because they’re emptier in winter doesn’t mean they disappear.
Many cafés will offer blankets (or at the very least, a heater) to help folks keep warm.
In the winter, terraces tend to become the smokers’ domain (even more so than in the summer). I remember, once, a visiting friend complained about the smoke when we sat outside; I wasn’t sure how to tell her that these tables were their last frontier – and were I to ask them to move, they’re probably laugh at me.
Despite the colder weather, I enjoyed dinner on a café terrace a few days ago, with a friend of mine. It was lovely and cozy – a completely different experience than sitting in the sun with a glass of rosé. But to be honest, I’m not entirely sure which I prefer.