Introduction: Understanding the physical capacity of people in different weather conditions can facilitate the assignment of right jobs to right individuals. People’s physical work capacity can change in response to weather conditions. Since military forces are usually obliged to work under different weather conditions, this study aimed to assess these individuals’ physical work capacity in desired, warm-humid, and very warm humid weather conditions.Materials and Methods: This cross-sectional study enrolled 36 military men (age: 20-29 years). Astrand treadmill tests were used to measure the participants’ physical work capacity, maximum aerobic capacity, and maximum oxygen uptake were measured under three weather conditions (desired, warm-humid, and very warm-humid).Results: The mean physical work capacity of the participants in desired, warm-humid, and very warm-humid weather conditions was 3.69 ± 0.52, 3.69 ± 0.55, and 3.41 ± 0.50 Kcal/min, respectively. The participants’maximum physical capacity under the mentioned conditions was 10.87 ± 1.54, 10.84 ± 1.63, and 10.02 ± 10.48 Kcal/min, respectively. Maximum aerobic capacity of the subjects was 29.52 ± 2.52, 29.76 ± 2.65, and 28.14 ± 2.76 ml/kg/min, respectively.Conclusion: According to our findings, people have similar physical work capacity under desired and warm humid weather conditions. However, physical work capacity reduced in very warm-humid weather.Moreover, the participants were allowed to perform light-moderate work during a work shift.