Abstract: Based on vertical profiles of relative humidity, water vapor density and liquid water with high resolution from ground to 10 km altitude, precipitable water vapor, path-integrated cloud liquid water and cloud base height data, combine with hourly rainfall data in Wuhan, three classes (19 cases) rainfall events with different rain intensities in the first hour are analyzed. Statistic results show that a significant increase of humidity in atmosphere and near the ground are necessary conditions before all classes of precipitation. The incremental centers of water vapor precede the incremental centers of liquid water for 0.5-1 hour below 2 km. At 1.5-1 hour before precipitation occurs, the growth rate of water vapor and liquid water change suddenly from a slow increase to a rapid increase. At 7 hours before heavy rainfall occurs, relative humidity saturated. Then, cloud base height decreases rapidly. Near heavy rainfall, the increase of path-integrated liquid water, water vapor and liquid water content in the lower atmosphere are significant with the maximum value and at the lowest altitude. Before weak precipitation, the increases of humidity in atmosphere and near the ground, water vapor and liquid water occurred earlier and are stable. Incremental centers with the minimum values and the highest altitudes result in the weakest raininess in the first hour. But, the high value centers maintain from precipitation start to 5 hours later, which leads to long time precipitation.