Peterborough has a humid continental climate (Köppen climate classification "Dfb") with four distinct seasons. It lies in a transitional zone between areas to the south, which have a milder winter climate, and areas to the north (within the Canadian Shield), where the winters are snowier and sharply colder. Peterborough's Hardiness zone is 5b. Peterborough's climate can be quite unpredictable and vary greatly from one part of the City to another due to the effects of the Oak Ridges Moraine and changes in elevation. In the South End and areas south of the City, the Moraine acts as a barrier for weather patterns moving off Lake Ontario, reducing precipitation. In the North and West Ends of Peterborough the effects of the Moraine are not as prominent, at times creating slightly cooler temperatures and more precipitation than the more southern parts of the City and County.