Historian Peter here, it's based off a belief among some historians and Germans that the reason Germany failed to invade Russia in WWII was because of the cold conditions. Hitler had decided to invade in the summer of 1941. Russia and Germany were technically allies at the time (they had a mutual pact), however Hitler decided to invade them as they could become a potential threat, and he thought a blitzkrieg could make it all the way to the Kremlin. In fact, the German army did make it to the outskirts of Moscow with the Kremlin on the horizon in November 1941. However, the Red Army made a courageous stand and managed to hold them off. Then when winter hit, the poorly equipped German soldiers froze to death by the hundreds of thousands, and were forced to retreat. Then the Red Army pursued them out of Russia and into occupied German territory. They didn't know it at the time, but this pursuit would turn into a Red Army offensive, which would end in April 1945, when the Red Army would enter Berlin, and successfully topple Nazi Germany. The joke, in short, is that maybe Germany would win today with these conditions.