A light, water-resistant, nylon cover for the windshield and side windows is the simplest and least expensive way to protect the plexiglass from ultraviolet light and the interior and avionics from excessive heat. These clip-on covers are typically light and compact and require minimal interior space.
The next step up is a sturdy canvas cockpit cover that adds some measure of wind and weather protection. By providing additional coverage area, canvas covers also help prevent water from entering the airplane through leaky door seals.
Quilted engine covers are essential for cold climates. They keep cylinder and oil temperatures warm during short periods of down time lasting a few hours. And they make engine preheaters far more effective prior to the first engine start of the day, thereby decreasing engine wear and improving reliability and longevity.
For airplanes that live outside—especially in harsh environments—full aircraft covers that protect the wings and fuselage can be a cost-effective alternative to hangars. In Alaska, where hangars are particularly difficult to come by and expensive, whole-airplane covers are the norm. And they do an admirable job of protecting both metal and fabric-covered airplanes from the elements year-round.
Just as pitot-tube and static port covers prevent water or bugs from compromising those critical aircraft systems, aircraft covers ranging from simple and light ones to whole airplane varieties can be essential equipment.