Based on the Northern Hemispheric snow cover data from 1973 to 1995, climatologic characteristics and changes of snow cover extent over the Northern Hemisphere, Eurasia and North America are studied. It is found that 1970s is a period of snow cover expansion with the maximum in 1978. After 1980s, snow cover decreased significantly. Correlation analysis shows that East Asia winter snow cover is negatively correlated to summer precipitation in the areas from the Mid-lower reaches of the Yangtze River to south of it. Spring snow cover is significantly correlated to rainfalls in northern Xinjiang and northern Northeast China. Significant reverse correlations were found between East Asia winter snow cover and the Meiyu duration when ENSO years are excluded.