dslr - How useful is silica gel for protecting SLR cameras against condensation from changes in temperature?

I am planning to travel to places like Switzerland (Mt. Titlis) which has temperatures going down to -15 C. I have the Nikon D3100 SLR camera. I am not sure about the performance of the camera in such conditions (and the precautions to take). I am planning to put 2 small pouches of silica gel in the camera case/bag.

How useful is the silica gel in protecting the camera for any kind of condensation issues that may arise due to change of temperatures?