Heat Stress

Heat stress is the combination of factors, including air temperature, air movement, humidity, radiant heat, and physical work that determine the total heat load on the body.  Heat stress may affect field workers, greenhouse staff, and pesticide handlers who are working in hot environments and/or wearing personal protective equipment (PPE).  PPE can limit the body’s ability to cool itself.

Heat strain is your body’s response to heat stress.  When heat stress is excessive, a person may feel uncomfortable and distressed and a heat illness can then occur.  The severity of heat strain depends on many variables, some of which you can control and some of which you can’t. These variables include age, level of physical fitness, level of dehydration, acclimatization, clothing, ventilation, and diet.

Be Aware!  

  • With mild heat-related warning signs symptoms often increase if action is not taken.
  • Heat can also cause safety problems.  You are more accident-prone while working in the heat!  Heat stress can affect your coordination, your concentration, reduce your strength and alertness, and make you irritable!  Avoid heat stress!

How to Avoid Heat Stress

  • Acclimatize.  Allow your body to adjust to the heat naturally and gradually; gradually increase the time you spend in the heat until you reach the total amount of time desired.  Most people acclimatize to warmer temperatures in 4-7 days.
  • Drink Water.  During hot weather, the body loses up to 3 gallons of fluid a day!  Drink cool water before, during and after work during heat stress conditions.  Drink at least 4 oz of water every 15 - 20 minutes during work, even if you’re not thirsty.  Don’t depend on thirst - you can lose 2-4 lbs of water before you feel thirsty!
  • Maintain Your Weight.  All weight lost due to sweating should be regained every day.  Weigh yourself every day and keep weight constant by drinking plenty of water.
  • Avoid Alcohol.  It causes dehydration - an added burden for your body in hot environments.  Don’t drink alcohol before starting strenuous physical work or exercise.
  • Use Salt.  Add salt normally to your food, but avoid salt tablets that may cause over salting.  Caution: Check with your physician about salt intake - especially if you have any heart or circulatory ailments, such as hypertension.
  • Plan Ahead.  Do the most strenuous exercise or work during the cooler periods of the day.  Pace yourself.
  • Eat Lightly.  Eat light, nutritious meals -- preferably cold.  Fatty foods are harder to digest in hot weather.
  • Rest Often.  Rest in the shade or in a well-ventilated room.  Short, frequent breaks are more effective than long, infrequent ones.
  • Wear the Right Clothes.  For outdoor work wear wide-brimmed hats, sunglasses, sweatbands, and proper footgear.  Breathable clothing will allow air to circulate better and sweat to evaporate faster.
  • Take Advantage of Cooling Systems and Shade.  Use fans, ventilation systems, and shade whenever possible.  Cooling vests and gel headbands and wristbands can provide additional relief.
  • Be Physically Fit.  One of the best protections against heat illness is physical fitness.  A strong heart is better able 1) to pump large amounts of blood to supply oxygen to muscles and 2) to pump large amounts of hot blood from your muscles to your skin, where the heat can be dissipated.

Heat Illnesses

Heat Cramps

  • Description: painful muscle spasms following hard physical work or vigorous exercise; can occur during work or rest; occur in calves, stomach muscles, back and arms; signs include headache and sweating
  • Cause: dehydration or loss of body salt in sweat
  • Treatment: rest and cool off; drink electrolyte and sugar fluid or water; stretch cramped muscle with one hand and gently kneed it with the other hand
  • Prevention: dink a cup of water just before you work in the heat and 1/2 cup every 15 minutes during work

Heat Rash 

  • Description: tiny red blisters on the skin and/or a pricking sensation during heat exposure
  • Cause: plugging of sweat glands due to unrelieved exposure to humid heat; skin is continually wet with un-evaporated sweat
  • Treatment: use mild drying lotions; keep skin clean to prevent infections
  • Prevention: wear fast-drying cotton clothing; cool sleeping area to allow skin to dry between heat exposures 

Heat Exhaustion

  • Description: sweating; dizziness; fatigue; nausea; vomiting; headache; fainting; rapid pulse; cool, moist skin; pale or flushed complexion; dilated pupils; near normal body temperature
  • Cause: sustained exertion in heat; failure to replace water lost in sweat; may develop slowly over several days if you lose more water than you consume
  • Treatment: remove to cooler environment; keep at rest on back with feet elevated; fan and sponge with cool water, cool damp cloths may be paced on neck, armpit and groin area; 1/2 cup of water every 15 minutes; seek medical attention this is a serious condition often leading to heat stroke
  • Prevention:  drink a cup of water just before you work in the heat and 1/2 cup every 15 minutes during work

Heat Stroke

  • Description: no sweating (or sweating profusely); hot, dry, red skin, high and rising internal temperature, pupils constricted; mental confusion, loss of consciousness, dizziness, convulsions, or coma; FATAL IF TREATMENT DELAYED
  • Cause: failure of sweating mechanism brought about by sustained exertion in unacclimatized workers; obesity, lack of physical fitness, recent alcohol intake, dehydration, and cardiovascular disease may be predisposing factors
  • Treatment: CALL FOR MEDICAL HELP IMMEDIATELY - BRAIN DAMAGE AND DEATH MAY RESULT IF TREATMENT IS DELAYED; remove to cooler environment; keep at rest on back with feet elevated; cool by any means possible - hosing, immersion, rubbing ice on the skin, or pouring any liquid over the skin; give nothing by mouth if the person can't drink; if able to drink give something to drink sports drink would be best; stop cooling as behavior is normal again
  • Prevention: monitor yourself while working in severe heat; drink a cup of water just before you work in the heat and 1/2 cup every 15 minutes during work


  1. About Heat Stress, Channing L. Bete Co., Inc/Kimberly-Clark. 1994 Edition. 
  2. Cornell University Heat Stress Factsheet. 
  3. Avoiding Heat Stress, U.S. EPA, 5/93. 
  4. First Aid Manual, American Red Cross, 1988.
  5. The Complete Sports Medicine Book for Women, Shangold, M. and Mirkin, G. Simon and Schuster. 1992. V: Feb. 4, 1998
  6. reviewed with Heartsaver First Aid, CPR, AED Workbook American Heart Association 2011