Players will be able to play as one of Napoleon's marshals and not just as Napoleon. One of the distinguishing characteristics of the Battle of Eylau, as I understand it, was a blinding snowstorm at one point. There certainly will be. The game wouldn't be the same if Prince Murat's Cavalry Reserve couldn't make that famous charge during the storm to maul the Russian center. The special rules for this game have taken that into account and the PC version will also.
Rules account for three types of weather.
There is clear, snow, and blowing snow. Blowing snow was what Murat's horsemen charged through. The weather makes the game really interesting. If the weather stays clear for most of the battle the Russians will actually enjoy the advantage. With weather like blowing snow the French do.