An Alberta Clipper is a type of low-pressure weather system that forms in Alberta or nearby, on the eastern side of the Rocky Mountains. It is a fast-moving storm, hence the name “clipper,” which refers to 19th-century ships known for their speed. Depending on the province where the system approaches the Canada-United States border, sometimes it is called a Saskatchewan Screamer, Manitoba Mauler or Ontario Scary-o. It may also be called a Canadian Clipper or simply a Clipper. Such storms mostly occur in December and January but are common in the fall and spring, too. They form about 5–20 times per season.