Why people put up their windshield wiper when their car is parked under the sun?
It is likely that these car owners do not wish dirt and dust to rest on the windshield wiper arm's position on the window. The dirt and dust mixed with water (from rain) can affect visibility. Of course, this can easily resolved by cleaning the wiper arm.
I depends on how hot it is outside. I've seen wipers melt and stick to the windshield. When you turn them on or lift the wiper arm the rubber end stays stuck to the windshield and comes right off the wiper blade.
It's not only when it is sunny it is also when it is snowing. This helps extend the life of the wipers. I know it sounds strange, but it really does, when it is a hot sunny day out, removing the rubber wipers from the windshield prevents the rubber from losing its edge. In the winter, it keeps the blades from being damaged when you scrape the ice of the window. Also from freezing and not working properly.
