Ambient temperature and relative humidity showed a direct effect on breeding efficiency. Heat stress reduces the intensity and duration of oestrus at temperature-humidity index (THI)>25 in hot and <25 in cold seasons. Contrarily, there is a tendency for better performance during the cooler months. Generally, it seems that a number of factors, singly or in combination, cause the marked seasonal breeding behaviour. Management, housing and photoperiod may be of the factors that change the manner of manifestation of oestrous symptoms during summer months. Exposure buffaloes to the latter conditions evokes a series of drastic changes in the biological functions that include depression in feed intake, efficiency and utilization, disturbances in metabolism of water, protein, energy and mineral balances, enzymatic reactions, hormonal secretions and blood metabolites. Such changes result in impairment of production and reproduction performance. The effect of heat stress is aggravated when heat stress is accompanied by high ambient humidity.