Some seed like switchgrass seed is harder and "tougher"...naturally designed to last thru punishing winter weather and not germinate until warm late spring weather brings the stratified seed to life...however...
clover seed isn't designed quite that way and can literally rot thru the severe freezing, cold wet, thawing, etc. of a long mid-west winter. Sowed heavy enough some will no doubt survive but...
for best results wait until Feb/March and sow on bare ground (some say snow is ok...but if it melts fast....) the light freezing/thawing weather will just work the seed into the soil (enough to make seed/soil contact) and 30-60 days later warm weather will have it germinating and on it's way.
if in your case you are unable to make it back down to seed in late winter and you want to chance it...let us know how it works...who knows...you may teach an old dog (no comments please /forum/images/%%GRAEMLIN_URL%%/blush.gif ) new tricks! /forum/images/%%GRAEMLIN_URL%%/smile.gif