As always you drive to the conditionsYes they are, tests show that stopping distances in summer on wintertires can exceed 20-30 meters, compared to good summertires, and that's a loooooooong distance at an emergency stop!!!
Like I said I'd only do it if I came to the end of winter and the tyres were close to the end of their life in terms of being good for use in the snow. I just think it's a waste getting rid of tyres which are perfectly useable, just not in snow which to be fair isn't all that common in the UK