From my limited experience of temps down to minus 20 oC and biking down to -7 oC ( not including wind chill where present) .... use Gortex , slightly loose fitting gloves, and stretch your fingers and wrist now and again to improve the circulation ... and keep a pair of silk liners for the really cold stuff of minus 20-30 oC... that lot will keep your hand toasty warm .... . Richard