Frank Uhlig , Nov 11, 2004; 04:12 p.m.
Let the camera/lens adjust to the new temp slowly.
If I walk from a cold room 60 degrees into summer 100 degree weather, my glasses always fog up, those on my nose. But the ones in my case do not fog if I take them out a while later.
Same principle works for lenses. So wait to take your lens out; 2 minutes or 20 depending on degree of temp change.