It is a well known fact the gel point of biodiesel is higher than that of petroleum diesel. That would tend to suggest that it is less suitable for cold weather use. But according to the National Biodiesel Board, as long as precautions are taken such as using high quality fuel and following proper blending procedures, biodiesel blends are reliable even in sub-zero temperatures.
To further illustrate that point the National Biodiesel Board has compiled a list of fleets around the country that are using biodiesel in cold weather environments.
National Biodiesel Board - Cool Customers
They also have written a feature article on Cranmore Mountain Resort, which is using B20 (a blend of 20% biodiesel and 80% petroleum diesel) in their ski slope grooming equipment.
Biodiesel Stands Up to Sub-Zero Temperatures