Analysis of rainfall and temperature patterns on yam yield in Lafia, Nasarawa State, Nigeria. Variability is one of the serious environmental challenges that has received a lot of complaints. This study therefore sought to examine the effects of climate variants on yam yield, data were collected for a period of 15years from the Nigerian Meteorological Agency (NIMET) and the Nasarawa Agricultural development Project (NADP) in Lafia, capital of Nasarawa State. The data were analyzed using the Pearson correlations and linear regression analysis and the trends in temperature, rainfall on yam yields. The result of the study shows an increase in maximum and minimum temperature at 0.1680C and 0.4130C respectively, coupled with unreliable rainfall of 0.079 over the investigated period (2001-2015), while the standardized coefficient Beta was 0.075. The study indentified poor yield as the major effect of rainfall and temperature variations on yam yield. Maximum temperature had a weak (0.168) positively significant relationship on yam yield for the investigated period, minimum temperature had a weak (0.413) positive significant relationship on yam yield which is more advisable and rainfall had the weakest (0.079) positive significant relationship and it cannot be held responsible for higher crop yield, except if joined with other factors like soil fertility, soil moisture, soil pH, and so on for the 15 years period. It was recommended that crops like yam should be planted in the month of February due to enough heat absorption so it could rapidly grow when the first or early months of rains start, and that Agricultural Extension Officers should be deployed to guide famers through routine visits, sensitization programmes on variability in rainfall and temperature characteristics, use of farm inputs and monitoring of crop-climate relationships in the area in order to achieve improved crop yield.