When we were in Oregon recently we stayed near Mt. Hood. Not too surprisingly, the weather was a little variable although it was more cloudy, cool and rainy than warm and sunny. These two photos are of the same scene taken on different days. In the first photo the fog (cloud) has come down but it is not cold enough at ground level to cause any other effects. In the second photo, the fog/cloud has again descended but this time the temperature at ground level is below freezing and as a result the trees have become coated with ice.