The researchers analyzed 50 years of precipitation data in Hebei Province. They found that most rain falls in summer, with an average annual precipitation above 500 mm in most areas. Overall, there is a slight decrease in yearly rainfall, especially in flat regions. The plains have a 10-year precipitation cycle, while mountains have a 15-year cycle. Rainfall is expected to remain low in the near future. There were significant changes in precipitation levels in the late 1970s and late 1990s in Hebei Province.