Breaking a bone is a bummer, but it's even more aggravating to keep that cast dry for weeks or months while the bone heals.
Now, a new type of cast liner can actually get wet. The Gore Procel cast liner is made by the same company that makes breathable and waterproof Gore-Tex fabric. The product is wrapped around the broken part as usual, and then encased in a fiberglass cast. The liner dries by evaporation in about an hour, meaning you can bathe and even swim without a problem.
So now, summer isn't the wrong time of year for a broken bone any more.