The relationship between periodic fluctuations of pressure and precipitation was investigated using the continuous wavelet transform and wavelet coherence transform methods for a rainstorm case that occurred during 19–25 June 2005 in Guangdong Province, China. The results show that a period of 2–4 h existed in both pressure and precipitation fluctuations. Furthermore, this high frequency pressure fluctuation was closely related to the fluctuation of precipitation with a similar period, and the fluctuation of pressure was about two hours ahead of the precipitation fluctuation variation. Since the high frequency pressure fluctuation implies the existence of gravity wave activity, the results suggest that gravity wave activities with a 2–4 h period in the atmosphere exerted an important influence on precipitation during this rainstorm.