Abstract: Although the relative humidity and wind field in lower atmosphere were very effective to forecast rain or shine weather, there were still some missing or false-alarm forecasts. In order to improve the accuracy rates of rain or shine weather forecast in Heilongjiang province, the forming reasons of weather cases with and without rain were analyzed. The results indicate that the temporal and spatial distributions of K index are indicative to rain or shine weather forecast, and could help to forecast the complex weather condition in which relative humidity in low level is small or wind convergence is poor, which are easy to lead to a missing or false-alarm forecast. Precipitation often appears in the high value center area or high energy tongue area of K index and in the strong K index gradient area or energy front, while it is seldom in the low value center area of K index. The threshold values with or without rain in the high and low values area of K index vary in different seasons.

Key words: font-family: "Times New Roman", mso-font-kerning: 1.0pt, mso-ansi-language: EN-US, mso-fareast-language: ZH-CN, mso-bidi-language: AR-SA,  High value area of K index')">mso-fareast-font-family: 宋体"> High value area of K index, K index')">Low value area of K index, Energy front