Abstract: Chilling in May causes damages on early rice in the double cropping system.Basing on the local standard of Hunan province(Meteorological Disaster Terminology and Classification),the spatio-temporal variations of chilling in May was analyzed systemically for 96 stations over Hunan in the period 1961-2009.Timing and extent of chilling in May were considered to improve the calculating method of cold accumulated temperature and establish cold accumulated equivalent temperature.Considering the current status of early rice cultivation in Hunan,meteorological risk of chilling in May was quantitatively evaluated by using its intensity index.The result showed that the western Hunan was at the high risk of chilling in May,but the early rice production was little affected by low temperature because of its small rice area.The north and middle of Hunan where early rice mapping in large area was at higher risk of chilling,however,the southern Hunan was reversed.Finally,reasonable suggestions on cultivation of double cropping early rice were given in this paper.

Key words: Chilling in May, Chilling in May, Cold accumulated equivalent temperature, Risk evaluation, Early rice production, Hunan