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Insufficiency in the production of food crops in Nigeria has been linked with variation in rainfall features. This paper examined the impacts of variation in rainfall onsets, cessations and length of growing season on yam yield in Kwara State, Nigeria to proffer a solution to the problem of food insecurity in the state. Rainfall data were collected monthly for six stations in Kwara State between 1961-2017 (57 years). Yam yield data were also collected for the same period. Since no separate record of yam is kept for each climatic station, mean climatic data were calculated to match the yam yield record obtained from the above stations. Rainfall onset, cessation and Length of Growing Season (LGS) were calculated from monthly values. Decadal partitioning of both the crop and rainfall features was made to show variations. Time series analysis was employed to study trends. The strength of the relationship between the length of the growing season and yam yield was also conducted using correlation analysis. The result showed an upward trend of onset of rain coupled with a downward trend in late cessation of rain and a decline in the length of the growing season. On a decadal basis, increasing frequency of delayed onset of rain and late cessation was observed. Length of growing season exhibits a positive (r = 0.455**) relationship with yam yield. Suggestions were made on how to attain sustainable efficient yam cropping in the study area.