Context: Manual cutting of sugar cane requires intense physical efforts (physiological overload) which, if added to high environmental temperatures (thermal overload), elevate body temperature and expose workers to the risk of heat stress. Among the protective measures required to control the risk of heat stress is the limitation of working time, by implementing regular breaks during the work activity. Objective: To assess the risk of heat stress in the activity of manual cutting of sugar cane and set the pauses necessary to alleviate this risk as specified in Chart 1 of Annex 3 of the NR-15 and item 31.10.9 of NR-31. Method: We measured in locu, in several work hours, environmental variables (globe temperature, dry and wet bulb) and heart rates of cane cutters, which allowed us to calculate the Wet-Bulb Globe Temperature (WBGT) and cardiovascular load, respectively, used as parameters of thermal and physiological overloads, according to the American Conference of Industrial Hygienists (ACGIH). Results: WBGT exceeded 25°C in at least one of the times of day in 7 of the 10 assessed days, which evidences the existence of thermal overload on most days. Cardiovascular loads remained above the recommended limit for all evaluated workers, which shows the existence of physiological overload. Conclusion: In the conditions of the study to control the risk of heat stress on manual cutting of sugar cane, breaks are needed about 18 minutes to every 42 minutes worked. 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