The temperature and other meteorological elements of 36 years at Beijing Observatory are analyzed, so to understand the extent and temporal variation of hightemperature weather in midsummer (dog days) in Beijing. The results indicate: (1) The mean temperature and relative humidity in dogdays are 0.8 ℃ and 5% higher than those of the whole summer, respectively. (2) The mean temperature of “short dogdays” is 0.6 ℃ higher than that of “l(fā)ong dogdays”; meanwhile, the mean relative humidity of “short dogdays” is 5% lower than that of “l(fā)ong dogdays”. (3) The variation rates of the mean temperature, mean relative humidity, and mean rainfall are 0.42 ℃,－3.13%, and －11.25 mm per year, respectively. The findings can provide scientific bases for meteorological service for water resources, power supply, and traffic management departments, as well as the health care of people in Beijing.