Although a few records exist of ruby-throated hummingbirds in our area into December, as a rule, all of our hummingbirds are gone by mid-October. Their food isn't present in abundance and they go torpid in the cold--which can't be good for avoiding predators.
But as all birders know, birds don't necessarily do the things we expect. I am providing a link, sent to me by Elizabeth Hawley with some photos of hummingbirds at feeders in the snow. But you can see that the photographer made some effort to make things more hummingbird friendly by supplying cover and a heat source.