Winter is perhaps the only time you can successfully invade Russia. Hitler and Napoleon invaded in the summer and failed. The Mongols invaded in the winter and won.
Necessary, but not sufficient condition though.
Sweden tried in the winter, and failed for example.
How'd that work out for Napoleon and Hitler, just to name a couple.
Found: https://www.wikipedia.org/wiki/Invasion_of_Russia
But can't be arsed working out which started in winter vs which where destroyed by winter.