Abstract: Forty years data (1956-1995), mainly monthly mean values of minimum and maximum daily temperatures records have been analyzed for Mehrabad, a station in the West of Tehran and Varamin, a small town Southeast of Tehran as a rural site, to look for urban climatic change. This has included the long period of annual, seasonal and daily trends. The trend is predicted by a least squares regression analysis and the significance of the observed trend is calculated by using the Mann Kendall technique. The records show that on average the annual minimum temperature has increased specially for Tehran station (typically 0.065°C year-1). Temperature trends for nighttime are steeper by about twice as large as that of daytime trends for Tehran station. The mean temperature rise for the Tehran station is largest in Autumn and is weakest in Winter; while the steepest trend in minimum temperature occurs in November. The difference in the annual mean daily minimum temperature of Mehrabad and Varamin has increased with population. Closer examination of the records shows that the trend varies during this period in response to different rates of urbanization that shows weaker variations during the period from late fifties to early seventies than the period from early seventies to the early nineties. The Mehrabad wind speed records, during this period show that the Northerly component of wind at night has been reduced indicating the surface aerodynamics resistance increase due to built up areas.