The heat stress indices (HSI) combine the effects of both temperature and relative humidity, and classified as alert, danger, and emergency zones - See more at: file:///C:/Users/Nutthapon/Desktop/Heat%20Stress%20Index%20Chart%20for%20Swine%20Producers%20-%20The%20Pig%20Site.html#sthash.VDGfE3Ve.dpuf