Depending on the type of cover you are interested in, it could guard against sun glare, wind, rain, snow, UV rays, pollen, and dust. The clear ones are the best for rain, and the cloth is terrific for colder weather or wind. Even if the weather is good, you will want to have a sunshade of some sort to keep the harmful rays from affecting the child. A simple blanket is not the best protector from the elements, especially in hotter climates and seasons. It can be moved by the child and go unnoticed by the parent when moving the stroller.