Studies have revealed that the pattern of rainfall will change in view of climate change scenario being experienced globally. Thus, a thirty-year (1989-2018) rainfall data analysis was conducted for Iwo in Osun State, southwestern Nigeria to determine the trend pattern of rainfall. One parameter Mann-Kendall statistic was used in the analysis of the data. The results showed that while five months (February, April, July, August and December) showed negative trend (Negative y-values) indicating declining rainfall over the period, seven months (January, March, May, June, September, October and November) revealed a positive trend (positive y-values) implying increasing rainfall over the period for those months. However, the general analysis of the 30-year data showed that there was negative trend in rainfall in the study area which means that there is general fall in the rainfall incidence over the period in Iwo. The results of monthly trend indicated that rainfall is no longer dependable for a viable agricultural practice, and so water conservation methodologies need to be embarked upon in order to salvage crops from the shortfall in the rain caused by climate change. It is therefore, recommended that shifting in the planting dates, irrigation, planting cover crops and planting heat tolerant crops and early matured crop varieties among others should be considered by farmers, especially the small scale farmers. Stakeholders in water resources management holds the responsibility on averting water scarcity and the challenge of water pollution in view of the erratic rainfall to ensure human survival.