The observational climate data during 1961－2008 are used to investigate the features of the seasonal and interannual variations of temperature, precipitation, relative humidity, and wind speed over the urban and rural areas in Beijing and the effects of urbanization on the regional climate in Beijing are discussed. The results show that, over the past half century, the average temperature has an increasing trend, in particular in the winter season, and there is a weaker signal in the summer season. By analyzing the decadal variations of the temperature, it is found that this increasing trend has become stronger in recent decades, enhancing the effects of urban heat island, especially after the 1990s. Both the maximum and minimum temperatures show increasing trend in recent 48 years and the urbanization has the most important effects on the minimum temperature followed by the average temperature, and has the weakest effects on the maximum temperature. For precipitation, there is a decreasing trend, in particular for the summer season. Over the urban areas, both wind speed and relative humidity show decreasing trend which is closely related to the urbanization, especially to the changes of the surface types.