黄河许多河段在冬季都要结冰封河，由于黄河流经的地理位置和纬度不一，特别是兰州到内蒙古河口镇、郑州花园口到入海口两个河段，流向都是由南向偏北流动。冬季气温上暖下寒，封河自下而上，冰层下厚上薄。到了第二年春季，封河的冰层融化，由于气温是南高北低，开河自上而下 Due to the geographical position and latitude of the Yellow River flowing through many sections of the Yellow River in winter, the Yellow River flows from two directions, namely, Hekou Town in Inner Mongolia to Hukou Town in Inner Mongolia and from Zhengzhou Huayuankou to Haikou. The flow direction is from south to north North flows. Winter temperatures on the warm cold, closed down the river, thin ice thickness. The next spring, the ice melt in the closure of the river, due to the temperature is high from north to south, start from top to bottom