Abstract: Based on the daily precipitation data from 10 automatic weather stations from 1961 to 2009 in Yili area, the temporal and spatial distribution of the inter-decadal, annual, monthly rainstorm days and variation of their cycles were analyzed using methods of a linear trend, a cumulative anomaly, an M-K test, and a cycle analysis. The results showed that the rainstorm days are in an increasing trend in the recent 49 years in Yili area, and its linear trend increases 0.107 days every decade. Rainstorm occurs mainly during May to July which accounts for 73.2 % of the total, especially in June, then in July. The year with the abnormal fewer rainstorm day is 1995, while the years with the abnormal more rainstorm days include 1996, 1999, 2002, 2003 and 2007. The rainstorm days gradually increase from west to east and from north to south. There is a 2.8 years cycle for the annual rainstorm days.

Key words: Rainstorm day, Spatial and temporal distribution, Abrupt change test