Hourly values of relative humidity that have been recorded at 76 stations across the country were closely examined. Daily averages were computed for four periods in a day: morning, afternoon, evening and night. Linear trends were analyzed for each season over the past 50 years. Preliminary results reveal a significant decrease in relative humidity during the winter and spring in all regions while little change has occurred during the summer and fall. Attempts to explain these results by comparing trends in the dry bulb and dew point temperatures will be presented.