Abstract: By using more than 50 years climatic data of the daily temperature and precipitation at 96 weather stations in Hunan province,the methods of definition of low temperature,snowfall,freeze-up,frost indexes were confirmed.The space distribution,duration,historical intensity and disaster impacts of low temperature sleety frozen disasters in Hunan province in early 2008 were comprehensive analyzed.The results showed that this low temperature sleety frozen extreme disaster weather rarely happened since the entire meteorological records in Hunan province from the middle Jan.to the early Feb.in 2008.The maximal persistent low temperature days,the longest persistent freeze-up days and the maximal persistent frozen days were the maximum values compared with the same historical periods since 1951.It was considered as the extreme climatic disaster by synthesizing various indexes and statistics.The characteristics of the disaster were intensively temperature falling,widely impacts,long duration and high intensity,resulting in great impacts on agriculture,forestry,electric power,transportation and people's daily life in Hunan province.

Key words: Low temperature freezing, Disaster weather, Climatic characteristics, Impact assessment