Abstract: The analysis of trends in temperature, precipitation, and relative humidity and evaluating their statistical significance have recently received a great concern for the assessment climate change effects. This research is to analyze a long time record of surface relative humidity for four cities, representing different climate zones, in Iraq using NCEP data. Parametric linear regression and nonparametric Mann–Kendall tests were applied for detecting monthly and annual trends in the relative humidity. The monthly time series showed that relative humidity is decreasing during winter, spring and autumn months. The decreasing trend during summer months is relatively weaker. This because summer in Iraq is hot and dry so changes in relative humidity is small. The annual relative humidity also exhibited a decreasing trend for the four cities. The results also illustrated that the deceasing trend in relative humidity is relatively stronger for Mosul because of it rather cooler climate and relatively smaller for the southern city of Basrah.