The National Weather Service uses a "heat index" that alerts the public when combinations of heat and humidity could make hot weather hazardous. The index was primarily intended for general public use but it can be useful in evaluation of occupational exposures. When weather conditions warrant, increased attention must be paid to the prevention ho heat related illnesses and the appropriate steps taken to reduce the effects of heat and humidity. The index, also referred to as the "apparent temperature", is a measure of the contribution humidity makes to high temperature to reduce the body's ability to cool itself and is explained it the chart below.

NOTE: When the air temperature is above 80 degrees F. and the relative humidity is above 40% the temperature the body experiences is greater than the air temperature.

• Heat Rash - also known as prickly heat, occurs when people are constantly exposed to hot and humid air, causing a rash that can substantially reduce the ability to sweat. Heat rash is not just a nuisance because of discomfort, but by reducing the ability to sweat, the ability to tolerate heat is reduced
• First Aid - Cleanse the affected area thoroughly and dry completely. Calamine or other soothing lotion may help relieve the discomfort.

• Heat Cramps - may occur after prolonged exposure to heat. They are the painful intermittent spasms of the abdomen and other voluntary muscles. Heat Cramps usually occur after heavy sweating and may begin towards the end of the workday.
• First Aid - Rest, drink plenty of water. Water is recommended but electrolyte fluids may be used.

• Heat Exhaustion - may result from physical exertion in hot environments. Symptoms may include profuse sweating, weakness, paleness of the skin, rapid pulse, dizziness, nausea, headache, vomiting, and unconsciousness. The skin is cool and clammy with sweat. Body temperature may be normal or subnormal.
• First Aid - Rest in the shade or cool place. Drink plenty of water (preferred) or electrolyte fluids.

• Heat Stroke - is a serious medical condition that urgently requires medical attention. Sweating is diminished or absent, which makes the skin hot and dry. Body temperature is very high (106 degrees F. and rising), and if uncontrolled, may lead to delirium, convulsions, coma, and even death.
• First Aid - This is a Medical Emergency!! Brain damage and death are possible. Douse the body continuously with a cool liquid and summon medical aid immediately.