In the Great Northern War scenario, starting in October 1708 very harsh weather conditions ensue and continue throughout the ENTIRE year of 1709. Yes, the winter of 1708-1709 was brutal, but there weren't blizzard conditions EVERYWHERE in July or August! I wasted an entire year of game time just twiddling my thumbs and pressing the end-turn button waiting for the funereal white to disappear from the map. Yet, June, July, August, September came and everything was still "very harsh conditions."
Someone mentioned this issue on the Matrix forums and Ageod turned-out a quick fix for the 1709 Spanish Succession scenario, but apparently this issue somehow slipped through the play-testing for the Great Northern War scenario. (It's probably in the other scenarios as well.)