There are several different types of awning cover materials that are waterproof. The most effective material at keeping out water is vinyl. Vinyl does not allow any water through it, but awnings made of this type of material tend to absorb heat. Therefore, they could get hot if you are sitting underneath them on a sunny day.
Some forms of acrylic awning are also considered to be waterproof. If you are looking for a very durable, waterproof option, the aluminum awning is also tough to beat. Aluminum awnings are very hard and non-porous, which means they will not allow any water through.