Ground observation data at Yinzhou weather station in Ningbo were used to study changes in precipitation and temperature during high-temperature periods. Trend analysis,mutagenesis analysis and correlation analysis were done. It was found that from 1961,temperature and precipitation in Ningbo showed a constant increase trend, while relative humidity decreased progressively. The rise in temperature was a key factor for decrease in relative humidity. Relative humidity changed abruptly in the early part of this century. Relative humidity decreased more obviously from then on. The climate had become warmer and drier. Temperature and relative humidity showed a significant negative correlation in high-temperature periods from 2000 to 2013. The correlation coefficient between temperature and relative humidity was the highest value of 0. 633. High temperature weather is a crucial factor in the obvious decrease in relative humidity in these years.