Background: One of the biggest global occupational threats, especially in the outdoor workplace, is climate change and global warming, as workers are exposed to the heat stress leading to reduced performance. The aim of this study was to investigate the effect of workplace climate on labor productivity index in the agricultural sector. Methods: In this study, data related to environmental variables of 215 synoptic meteorological stations in Khuzestan province were collected from three climatic regions (hot, mild, and cold). Using MATLAB R 2018b mathematical software based on ASHRAE/ISO7730 standard values by designing some scenarios, predicted mean vote (PMV) index, and then, labor productivity index (P) were estimated. The data were analyzed using SPSS version 25 software. Results: The results showed that in the hot regions, there is a significant inverse relationship between P index and the main environmental variables (ta, tr, pa). In the cold regions, increasing the amount of ta and tr in light and medium workload improved the P index, but for heavy workload, it reduced productivity, and the most effective factor was increasing air vapor pressure. In the mild regions, the most effective factor in productivity was air vapor pressure. In addition, the results of Spearman's correlation coefficient showed that PMV index has a direct and significant relationship with P index. Conclusion: Regarding the increasing trend of climate change and its effect on the desired thermal comfort and productivity, well structure and planning is needed to manage farm workers health.