Depending on the format of the Pergola it can offer protection from a very light rain but they are not normally designed to be rainproof. As an airy open structure with a lattice style roof that lets light below and hot air to escape, they do not block the rain. For a solid rainproof roof, you may prefer a Ramada or Gazebo. See the FAQ above for What is the Difference Between a Pergola, Ramada and Gazebo. As with anything, there are lots of examples that do not fit the rule! There are now many companies that offer rainproof covers for Pergolas or retractable installations that can give you the same look and feel of a Pergola but the added benefit of being rainproof when required.