winter walks with baby

Ah
im due chriatmas eve and we live in minnesota.  its gets cold and snowy here. i wouldnt consider taking him out if its snowing or too cold. but when do you think a good time to start walking is? i cant just wait for spring lol because in MN spring may not come until June!  
i was thinking he'd be ok at 4 weeks. what do you think? when did your babies get to see the light of day??