Basically, no snow in May, no blizzards in October, increased chance of Mud on Mud months and increased chance of clear skies at the top of the table. Also I'd suggest that the European Weather Zone, instead of being the base for the table, be -2. Though I realize European weather includes Hungary, the Crimea, Romania and other places with poor road conditions (at the time). The brunt of fighting in this zone would naturally occur in Germany and Poland, where Rasputsia wasn't a problem, so the chance of mud should be vastly decreased there.
