The changes in the environmental factors like ambient temperature, relative humidity, wind speed and solar radiation causes stresses in lactating cattle. Heat stress is a condition in which the animal body has problems dissipating excess heat. Results of inadequate heat dissipation range from general discomfort to symptoms of heat rash, heat syncope, heat cramps, heat exhaustion and heat stroke. Heat stress assessment methods were carried out using some equations presented temperature-humidity index (THI) or heat stress index (HSI) or using different heat index charts. Temperature Humidity Index is calculated based on the relationship between environmental temperature and relative humidity. The heat stress index is a simple combination of temperature and humidity and has been designed as a measure of animal comfort. Heat Index Chart is a chart used by dairy producers to estimate the severity of heat stress of a dairy cow. This chart utilizes ambient temperature and relative humidity, which are readily available to the dairy producer on a daily basis and indicate from slight to severe heat stress of dairy cattle from some equations