The influence of meteorological factors on acid rains is investigated on the basis of observation data on acid rains and environmental meteorological factors from the urban area of Hangzhou from 1996 to 2010. The research indicates that the low incidence of acid rains occurred under heavy precipitation weather, the lower pH value was more likely to happen in continuous rainy weather. The average pH of rainwater was low under north wind conditions, and high under southwest winds. The pH value of precipitation was as low as 4.51 and the incidence of acid rain was up to 85.3% under the control of high pressure in Hangzhou; the pH value peaked 5.11 and the lowest acid rain rate was 66.5% in thunderstorm weather. The results show that different weather types led to varying degrees of pollutant diffusion, dilution, and wet deposition, which are also the main reasons for acid rain pollution.