Rainfall variability is a critical factor shaping agricultural production in tropical dryland regions. This study analyzes the spatial distribution of rainfall and rice production, examines their relationship, and evaluates the temporal lag effect of rainfall on rice production across 22 districts in East Nusa Tenggara, Indonesia. Secondary data at the district level were analyzed using spatial mapping, Pearson correlation analysis, and lag analysis (n = 48 monthly observations). The results show significant spatial disparities in rice production, with higher output concentrated in western regions (notably West Manggarai and Manggarai) and lower output in eastern and smaller island districts. Correlation analysis reveals a lag-dependent relationship between rainfall and rice production: the contemporaneous correlation is weak and non-significant (r = −0.26, p = 0.074), while correlations strengthen substantially at longer lags, peaking at lag 3 months (r = 0.81, p < 0.001). This indicates that cumulative rainfall during the growing season, rather than rainfall in the harvest month, is the dominant factor associated with rice production. These findings emphasize the importance of integrating temporal lag dynamics into climate–agriculture analyses and provide a quantitative basis for improving agricultural planning and climate adaptation strategies in rainfed monsoonal systems.