The study investigated seasonal variation in outdoor thermal comfort in Makurdi from 1971-2010. Daily air temperature (0C) and relative humidity (%) of the study area were obtained from Nigerian Meteorological Agency Operational Headquarters, Oshodi, Lagos. Daily thermal comfort levels were computed from the obtained data using the temperature humidity index (THI). The THI values were then summed into monthly, seasonal and annual comfort values. Correlation analysis was used to determine trend in the level of thermal comfort from 1971 to 2010. The monthly variation of THI showed the highest THI of 27.2 in April and the lowest THI of 24.7 in January. The seasonal variation of THI indicated highest THI of 26.5 during the hot dry season and the lowest THI of 25.1 during the cool dry season. The annual variation of THI showed an increasing trend from 1971-2010 with a positive correlation coefficient (R2) of 0.018. The result suggest that human discomfort is common in April while January is thermally comfortable Seasonally, the hot dry season was associated with human discomfort whereas the cool dry season is relatively comfortable. The positive annual trend of THI suggested a progressive change from human comfort to discomfort in the study area. The study concluded that measures of ameliorating human thermal discomfort should be focused principally in the months of March and April which coincides with the hot dry season to minimize the negative effects of outdoor thermal discomfort on the socio-economic development in Makurdi.