During the winter months in Wisconsin, we never know what to expect for weather. Drivers hear snow is coming and the first thing they do is put their wipers up on their vehicle. They do this to prevent them from freezing to the windshield. When you put the wipers up, keep in mind that it is putting stress on the spring that holds the wiper arms against the windshield.
Leaving the wipers up exposes the plastic gears and other mechanical components. Those items could be weakened or damaged by forceful wind gusts. Exposing your wiper blades to the weather can also cause the rubber blade to be blown off.
If the wind does catch the wipers or someone bumps them, it can cause the wipers to slam against the cold windshield and crack your windshield.
The best way to keep the elements off your windshield and to save your wipers is to cover the entire windshield. You can use a blanket, tarp, or they even make covers you could over on amazon specifically made for this purpose.