How to acclimate to the heat and how it happens

by James Hubbard, M.D., M.P.H.

Pop quiz:

  1. Why are some outdoor workers more prone to heat strokes after the first hot spell in early summer than later when it gets even hotter?
  2. Why are there more heat strokes in Chicago when the temperature may be hotter elsewhere at the same time?


Much has to do with your body having time to adapt, otherwise called acclimatization.  It takes between eight and 12 days for your body to acclimate to higher temperatures so when those hot days hit, you’re not ready.  The body acclimates to heat by:

  • Triggering sweating a lower body temperatures and sweating more. The amount of total body sweat may double.  This is a great way to cool off by the water evaporating off your skin, but doesn’t work well with high humidity.  The sweat can’t evaporate.  A little breeze helps.
  • Conserving sodium.  More sweat means more sodium (salt) loss, so your body starts making sweat that contains less sodium.
  • Ramping up your heart’s efficiency by pumping more blood per heartbeat.  That way more blood can be delivered close to the skin surface for cooling.  The cooler blood then circulates to your inner organs. This is one reason the elderly and heart patients don’t do well (weaker heart pumping).
  • Using body oxygen more efficiently so metabolism works a little slower.  Metabolism produces body heat.  More efficiency, less heat.

How to Stay Safe in the Heat

To prevent heat-related illness, go slow when the weather turns hot.

  • Take breaks under the shade.
  • Do the heavy work before 10 a.m. or after 4 p.m.
  • Fan a little and be sure to drink lots of water.
  • Maybe add a teaspoon of salt to the first quart or two of water, or drink an occasional sports drink with your water.

It is a fact that most people who work outside in the sun get dehydrated due to sweating and heat.  You can easily lose a quart of fluids per hour or more.  Dehydration leads to increased body heat (it’s a physiological thing).  Most people don’t become thirsty until they’re already dehydrated. So make it a point to drink fluids, thirsty or not.  On hot days with heavy work, you may need a quart or two of fluids per hour of work to keep up.  Sipping a little at a time is just as good, as long as you get drink the same net amount.

By the way, check on the elderly and chronically ill during hot spells.  Make sure they’re getting fluids and breezes.  When the humidity and heat soar, though, even fans don’t work well for cooling.  During heat waves, see if they can spend time in an air conditioned area around midday at least.  If nothing else, placing cool wet cloths on the neck or under the arms helps.

Does anyone have further suggestions to stay cool?

Doctors and business owners: Send customized issues of My Family Doctor to your customers or patients. E-mail for details.

As with all information on this site, this article cannot replace professional, personal medical advice. Read more here.

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14 Responses to “How to acclimate to the heat and how it happens”

  1. Dr. J Says:

    I remember when I first moved to Florida how difficult the heat was. With time, I’ve definitely acclimated to it. It’s still HOT, but at least now I can function :-)

    Thanks for all the good suggestions!

    Dr. Js last blog post..Dr. J will see you now: On sports and sportsmanship

  2. James Hubbard, M.D., M.P.H. Says:

    Dr. J,

    It does explain why short-term visitors have to be careful. Thanks

    James Hubbard, M.D., M.P.H.s last blog post..Smart Balance Peanut Butter: Expert review – plus readers’ opinions

  3. Sagan Says:

    Great suggestions. It’s also important to take extra care of our pets in the heat! Taking them out for walks in the hottest part of the day is really dangerous.

    Sagans last blog post..Maintaining a Healthy and Realistic Attitude toward Body Image during the Summer Months

  4. James Hubbard, M.D., M.P.H. Says:

    Thanks for the reminder Sagan

    James Hubbard, M.D., M.P.H.s last blog post..Smart Balance Peanut Butter: Expert review – plus readers’ opinions

  5. Steve Parker, M.D. Says:

    I treated much more heat stroke and environmental heat illness when I lived in Pensacola, Florida, than I do here in the hot Arizona desert. It must be the humidity in Florida (sweating doesn’t cool you down), and people are more cautious in the desert.


    Steve Parker, M.D.s last blog post..Yo-Yo Dieting In Women Has No Effect On Death Rates

  6. James Hubbard, M.D., M.P.H. Says:

    Probably so Dr. Parker. High humidity can make a lot of difference.

    James Hubbard, M.D., M.P.H.s last blog post..Smart Balance Peanut Butter: Expert review – plus readers’ opinions

  7. Cynthia Says:

    Having a cooler in the car with ice packs to keep oneself cool helps too. I am from the north and TX is hot. I do home care nursing so am in and out all day. I toss and ice pack on the back of my neck while driving and slam some Gatorade.

  8. Jake Says:

    I get excessively hot and sweat profusely even in cooler temps. I’m 67 and although I am a type 2 diabetic and have high blood pressure they are well controlled. I workout for an hour or so daily at the gym and feel great except for the sweating. My work takes me outside in the Texas heat walking around inspecting buildings. With almost no exertion my clothes become drenched with sweat as soon as I start moving around even in mild temperatures. This morning in the low 60′s I was sweating like a pig after a few minutes walking around doing an inspection. It’s embarrassing! Is there anything I can do to lessen the problem?

  9. Lance Robinson Says:

    Hey Jake, i know it’s an old post, but thee only thing that will help with the sweating is to address its cause. If you get one of them neck wraps that stay cool and wear that, it makes a world of difference! I nice insulated cup of ice to chew on also does wonders in helping your body in the core tempurature regulation dept. I sweat like a pig too.

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