Abstract:  By using some statistical methods and based on the frost and temperature observation data during the period of 1980-2009 from 7 meteorological stations in Changdu district, a time series was established and the characteristics of frost variations and its response to the temperature variation in Changdu district during the past 30 years were studied. The results showed that the first frost date was postponed significantly, and the last frost date occurred earlier and the frost-free period increased dramatically by 36 days over the past 30 years. The tendency has been more significant since the beginning of the 21st century. Temperature increase in Changdu is the major reason for the first frost date delaying, last frost date coming in advance, and the frost free period extending. The mean minimum air temperature and minimum ground temperature are the most important contributors to the delay of the first frost date and the early coming of the last frost date. 

Key words:  First frost date, Last frost date, Frost-free period, Distribution characteristics, Tendency