Daily moderate resolution imaging spectroradiometer (MODIS) (Terra and Aqua) snow cover products are used to produce flexible multiday combinations for each hydrological year between October 2003 and September 2013 in northeast China. Compared with in situ observations, the daily and flexible multiday combinations achieve overall accuracy of 47.51 and 76.52%, respectively, which is of MODIS Terra and 30.57% of MODIS Aqua under all-sky conditions. Snow cover fraction, snow cover day map (SCD), snow cover onset date map (SCOD), snow cover end date map (SCED), and snow cover index (SCI) are then generated. The highest SCD, earliest SCOD, and latest SCED are always located in the southern edge of Da Hinggan Mountain and Changbai Mountain, followed by Xiao Hinggan Mountain. SCI negatively correlated with air temperature, with a correlation coefficient of () in snowfall season; SCI positively correlated with precipitation, but is insignificant at the 95% level. This suggests that snow cover is more sensitive to air temperature than precipitation. In other words, continuous increase in air temperature due to global warming in the long term will result in continuous reducing of snow cover, a gracious water resource for northeast China, although a relative decrease in air temperature in the recent 10 years has resulted in snow cover increase.