Temperature and wind are the major microclimate parameters that were considered in the microzonation of Washington State. Thermal movements associated with bridges and wind pressure loading for traffic signs, signals, and luminaires are major concerns in Washington. Air temperature data for 49 stations across the state were obtained and were converted to the corresponding composite bridge temperature values. Maps of maximum, minimum, and range of air and bridge temperatures were created to identify the temperature pattern of the state and also to develop an isothermal map of mean bridge temperature ranges. Wind microclimate study included an investigation into incorporating a three-second gust wind into the AASHTO standards for calculating wind pressure on structural supports of traffic signs, signals, and luminaires. The new value of Ch (boundary layer profile factor), the primary parameter that changes when using a 3-second gust, were obtained by comparing the velocity profiles for the hourly, fastest-mile, and 3-second gust wind speeds. Adjustment of the gust factor is also included.