Temperature humidity index

Temperature Humidity Index (THI) is used to assess the effects of heat stress on milk production. THI is determined by the relative humidity and air temperature. As humidity and temperature increases, cow comfort decreases as they find it steadily more difficult to cool themselves. For example Milk production begins to be affected above a THI of 78, which will occur at 27 C and 80% relative humidity or at 31 C and 40% relative humidity as shown in the table below.