Temperature has no effect on photographic IR film. The IR that constitutes hot/cold is way out of the range of photographic film.
I have seen IR shots of conifers in the snow, and it was really nifty to see white foliage with white snow. That was done with Kodak, though. Usually when I do it with a 092 filter and Efke or Ilford, the conifers will be a light grey. One time when I was underneath conifers, in the deep shade and the sunlight couldn't filter, the IR made things look like a white fairy land. You might want to look for settings like that. Remember to bracket N, +/-1, +/-2, and you should be good, especially for your first trip with it.