What Pace Should I Run in the Heat?

Heat and/or humidity increase the physical stress on the body and therefore, increase the intensity or effort of the run, which results in higher heart rates

Q I’m finding running in the summer heat to be difficult and am wondering why I am so much slower. What should my pace be during the summer if I normally run about a 6:00-minute kilometre? I am training for a 5K. Are there any workouts I can do that would help make running in the heat more tolerable? 

A Donna, you are not alone; many others are struggling and sweating right along with you! Summer is difficult because of extreme temperatures and high humidity in many parts of the country.

The biggest problem runners face when running in the heat is adjusting to the higher temperatures and humidity. When summer arrives gradually, temperatures and humidity levels rise slowly, which gives runners time to adapt and acclimate to this “new normal.” Unfortunately, summer many parts of Australia are hit with high temperatures and high humidity almost overnight, giving runners very little or no adaptation time.

Heat illness is serious, deadly serious, so, what’s a runner to do? First, slow down! And then, second, use these adverse conditions to your advantage.

Heat and/or humidity increase the physical stress on the body and therefore, increase the intensity or effort of the run, which results in higher heart rates. For example, let’s say your 6:00-minute kilometre in good weather elicits a heart rate of 120 beats per minute (bpm). Hot, humid weather can easily add 20 beats or more to a runner’s average heart rate. This means that the same run pace will now elicit a much higher heart rate. Your 6:00-minute kilometre may now elicit a heart rate of 140 bpm or more. The higher heart rate makes that 6:00-minute kilometre run pace uncomfortable; hence, we are forced to slow down. The “slow down factor” varies from runner to runner, but in general, slowing down 20 to 50 seconds per kilometre is common in hot/humid weather.

Runners hate slowing down because they fear losing their conditioning and/or not being able to achieve their goal race pace on race day. Put your fears to rest because you can turn running in the heat to your advantage. A large part of training is related to the heart rates achieved during training. Even though your training pace has slowed down, your heart rate will still remain in the 120 bpm range and possibly be even higher because of the adverse weather. Your body becomes conditioned to that heart rate range regardless of the actual run pace. When the weather cools down, and you run at that heart rate, you will find you are able to run your 6:00 pace and probably even a bit faster after slogging through tough conditions! Come cooler temperatures, you’ll feel like you lost five or 10 kilos overnight and have to be careful not to go out too fast on race day!

Now, the downside is that by slowing the run pace, training is not as specific. A slower run pace means specific muscle fibres may not get recruited due to the change in stride and therefore, these muscle fibres may not receive all the conditioning they normally would at the faster run pace. But, by focusing on your heart rate instead of run pace, you can learn to use hot weather to your advantage. It’s sort of like making lemonade out of lemons.

Along with slowing down run pace, here are some more tips for surviving the summer without derailing your training…


  • Run in the early morning or early evening when temperatures are at their lowest for the day. Be aware that “cooler” is a relative term. The morning may have the coolest temperatures of the day, but it typically has the humidity level of the day.
  • Hydrate, hydrate, hydrate and this means including some electrolytes whether from a sports drink or a supplement.
  • Wear appropriate clothing. Invest in high tech lightweight wicking fabrics, light colours and reflective markers.
  • Slow down. Use a slower training pace, train by how you feel. Add walk breaks, for example, run for 3 to 5 minutes, then walk for 1 minute. Or, run and walk using landmarks. Run to a mailbox or a driveway, then walk to the next one. And, if you absolutely can’t run in the heat, walk. Walking will maintain your conditioning until you are able to return to running.
  • Run indoors. If the weather is really intolerable, run on a treadmill or an indoor track. Add 1 to 2% incline to the treadmill to better simulate running outdoors.



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