fbpx Skip to main content

Running in hot and humid weather

By July 11, 20192 Comments
floris gierman running with a hat and sunglasses on

In today’s post and video we discuss in detail:

  • The impact of high temperatures and humidity on running performance. [1:10]
  • What happens in your body during heat stress? [4:13]
  • Should you adjust your aerobic training heart rate with heat and humidity? [5:42]
  • The dangers and signs of heat illness [6:29]
  • How to train on hot and humid days? [8:37]
  • Heat acclimation training [10:29]
  • Marathon cooling strategies [13:13]
  • Protecting yourself from the hot sun [15:33]

I often hear from runners who live in hot and humid climates, saying things like, it’s so hard to run in these conditions, especially if I try to run at low heart rate. During the winter months I often hear the opposite, it’s so cold or there is so much snow out where I live, it’s impossible to run in these conditions.

Weather stress is real. This can be caused by a variety of elements. From hot temperatures and high humid conditions, to extreme cold conditions with very low temperatures. Then there are also other elements such as wind, dew points, rain, snow, hail, ice on the roads, etc.

All these weather conditions can impact your perceived effort, your heart rate and your running pace. In this video we’ll review a few strategies about how to deal with hot and humid weather conditions in training and on race day, so you can still maximize your performance. 

The impact of high temperatures and humidity on running performance.

I want to share an example of how a difference in temperate can change your running pace at the same HR. Here is an example of two recent runs 1 day apart.

  • The temperature for the run on July 5th (Strava) was much lower than on July 6th (Strava).
  • I started both days with a warm up walk and transitioned into a jog. First 2 miles are still warm ups.
  • Mile 3, so 5km in, the pace on both days is still same at pretty similar HR. Then I started to feel the heat.
  • At mile 4 (6.4km) I was 36 seconds per mile slower in the warmer weather. 

When runs become longer, the weather stress can increase more. Let’s look at a run from a few years ago, the same route, 1 day apart.

  • At 3 miles / 5km, running at the same HR, my pace is now 1 minute per mile apart.
  • At mile 6, so 10km in, I’m running at the same heart rate 85 seconds slower on the warmer day, so almost a minute and a half. 
  • Here are the Strava details for both runs on July 8th and July 9th.
  • Keep in mind, I’ve trained myself slowly to be able to handle heat well. I do not recommend these tests, especially if you’re not used to running in the heat. 

What happens in your body during heat stress?

For humans to live, our body temperatures must be kept within a narrow range, between 95 Fahrenheit (35 Celsius) to 107.7 Fahrenheit (42 Celsius). There are many variations in outside temperatures and effort levels of physical activity. During exercise, the majority of our energy is used for heat management and a smaller amount to actually have your muscles move you forward. 

As your running effort level increases, the rate of heat production increases. The main cooling mechanism for the body is sweat evaporation. 
Some people are more affected by different weather conditions than others. The main difference is in the body’s thermoregulation, your water and electrolyte regulation.

Tim Noaks wrote about this in much detail in The Lore of Running. An important point he made:

Sweating does not cause heat loss, it is the evaporation of the sweat into the atmosphere that causes heat to be lost 

– Tim Noaks

So this phase change from liquid sweat to vapor is what extracts heat from your skin. Humidity is a measure of the water content in the air. If the humidity is high, the sweat can not vaporize from the skin, it only drips off the skin, without the cooling factor. 

Should you adjust your aerobic training heart rate because of the heat and humidity?

This is a question I receive frequently from athletes. No, you don’t want to adjust your training heart rate. Your body is under additional stress and tells your brain what’s going on. We want to run at the same, or lower effort levels, which often means having to slow down our running pace. For some athletes this might mean having to slow down further and take walk breaks to stay aerobic. 

Some athletes get very frustrated about hot weather conditions. There are several things you can do to help with this process to make it as enjoyable as possible. 

Let’s first talk about heat illness since this is a very important topic.

The dangers of heat illness

Heat exhaustion and heat stroke are very serious illnesses for athletes. This can happen during races, but also during training, especially on hot days. What happens is that athletes are unable to regulate their body temperature and dehydrate. 

Signs and symptoms of heat illness may include: 

  • fast heartbeat
  • fast breathing or hyperventilation
  • fatigue, more than usual
  • dizziness
  • feeling hot
  • heavy sweating
  • headache
  • nausea and vomiting
  • diarrhea
  • muscle cramps
  • pale skin
  • problems coordinating movement, so not being able to run or even walk
  • fainting  

This is the dehydration of body and brain. These symptoms can overlap with heat illness or be even more severe:

  • confusion and disoriented
  • can’t see clearly
  • seizure
  • coma

Do not under-estimate the severity of heat illness during races and even during training runs. Treatment could require medical attention to get your body temperature down as soon as possible. At most warm finish lines at races, there is a medical facility with a bath of ice. This is an effective cooling method to bring the body temperature down to below 38 celsius. Otherwise ice packs are another good way to lower your body temperature. 

The risk of heat illness

There are several factors that can impact your risks for heat related illness, such as: 

  • athlete’s size, larger athletes have higher chances of overheating
  • running speed and intensity
  • temperatures and humidity
  • drinking the right amount of fluids 

Adults over the age of 65 and young children have a higher risk for heat exhaustion and heat-related illnesses. Their bodies cannot cool down as easily.
If you recognize any of these signs or symptoms mentioned, don’t try to be tough, especially if you’re running alone. Stop running immediately to avoid things getting worse. 

How to train on hot and humid days?

  • Run early in the morning or late at night don’t run during the heat of the day
  • Run indoors on a treadmill you might want to consider joining a local gym for a few summer months, or buying a treadmill 
  • Adjust your pace according to effort level | Slow down your pace!
    • The brain constantly receives information about the temperature of your skin, brain and core temperature. When the temperature becomes too high in most runners, the brain subconsciously tells your muscles that you are tired, so you either slow down or stop running all together. With less effort, your body will produce less heat. Standing in the shade and in the wind can help speed up this cool down process, preventing heatstroke. 
    • So when training, keep your effort levels under control. Even at a slower pace, you’re still getting a great workout in.
  • Split long run in 2 shorter runs Instead of going for a 90 minutes run, just split it up, 45 minutes in the morning and 45 minutes later in the day.
  • Run in shaded areas as much as possible running in the sun can increase your skin temperature much more than the outside air temperature
  • Limit concrete runs this heat gets right back at you. Running on flat trails, grass and sand can be better options here
  • Don’t run in the heat if you are not very fit, if you’re not used to the heat. And especially when you have previously experienced heat issues. Some medication and supplements can also impact your heat regulation, so be extra careful there. 
  • When running in higher temperatures and humid conditions, Hydrate well, don’t overdo it.

Acclimate yourself with heat training

Let’s talk about heat acclimation in training for race day. You can pre-acclimate to heat by engaging your sweat mechanisms:

Running with many layers of clothing on

In a recent podcast with 2:21 marathoner Jason Cherriman he mentions going on some training runs with several layers of clothing on. This post and 5 minute video can be found here.

Sitting in a sauna to get used to the heat

Another option is sauna training. I have a sauna at home and this helps me get used to warmer temperatures, similar to overdressing for your training runs. 

In a short period of 7 to 14 days, this heat acclimation can already happen. You can either do this a few weeks before a race, or even in early stages of a training cycle and then repeat again prior to your race. 

A caution for both overdressing with many layers of clothing and also about sauna use. Gradually build this up, you have to be careful not to overdo this, especially when it’s already warm outside. In some places like Texas or India, you might not even need additional layers of clothing. Listen to the signals of your body. 

Benefits of heat acclimation training

  • It will lowers your core body temperature, which will help with cooling. 
  • You will lower your heart rate during exercise
  • You will increase your sweating rate, so you can run at higher intensities like Marathon pace and your body has the ability to cool itself more easily.
  • You will develop your sweat glands, what that means is you will retain more electrolytes and you decrease sodium concentration in your sweat. You don’t want to sweat out all you’re sodium. 
    • You don’t have to drink as much as non-adapted runners would, especially within a marathon.
  • It has demonstrated to improve your VO2 Max
  • It increases your blood plasma volume, so there is more blood to go around, which can only be good to get oxygen to the muscles.
  • It enhances blood delivery to the skin 

Marathon cooling strategies

  • Use the early race miles to warm up, so start at a slower pace, don’t do a long pre-race warm up
  • Run with a water bottle with ice. You can drink throughout the race and keep your head and neck cool as well. 
    • Stay hydrated well, before, during and after your workouts. But do not over drink either! There is a condition called Hyponatremia, when you drink too much water and your sodium levels are diluted. At the Boston Marathon and the London marathon, runners have died from drinking too much water and having extremely low sodium levels. Hyponatremia is more common in runners who had slower times and body-mass index extremes. 
    • There is no one size fits all for the amount you should drink. The drinking guidelines for most marathons have changed to drink to thirst.  Tim Noakes, a South African scientist and professor also mentions that a more reasonable approach is to urge runners not to drink as much as possible but to drink to thirst. No more than 400-800 mL/hour.
  • Manage your electrolytes and salt. You can either drink sport drinks with electrolytes, or take tables, gels or mixed powders. During a race I take some gels and depending on the temperatures, I also take a salt / electrolyte pill about once an hour. 
  • Do not overdress! I see many athletes running in several layers of clothes. It’s ok to feel cool the first few miles of a race. 
  • Keep your head and neck cool
    • Pour water over your head at aid states
    • Use an ice bandana or towel to cool your neck. Cooling the blood in the large arteries in the neck, which carry blood to the brain, can be an effective cooling strategy. 
  • Sponging the body, focusing on lowering the skin temperature
  • Use minimal sunscreen in key areas. If you have a thick layer of sunscreen all over your skin, the sweat can’t evaporate from your skin, that’s what keeps you cool. 
  • Run in the shade whenever you can
  • Use some cooling from the wind, so try not to run in a big pack of runners. I’ve noticed this can make a big difference in temperature feel. 

Protecting yourself from the hot sun

  • Dr. Phil Maffetone shares several great insights about sun exposure and protection in his Big Yellow Book of Endurance Training and Racing, I can highly recommend this book. 
    • One observation he made is that healthy athletes don’t burn nearly as much as those who are less healthy
    • He mentioned that by maintaining a good balance of fats, especially including fish oil, you can control inflammation and protect yourself better from a long day in the sun. 
    • Antioxidants, vitamin E complex and vitamin C can also help protect the skin. Consuming enough vegetables and fruits will help as well.  
    • Many people are deficient in Vitamin D, this may cause you to get sun burned faster
    • Some people burn much more easily than others, for example extremely light skinned people, those with red hair or freckles
  • Some skin areas burn faster than others, I’ve noticed this myself as well. Your ears, nose, lips, neck and head are more sensitive, so it’s good to wear protective clothing and a hat and / or bandana for your neck. 
  • Sunglasses are important to protect your eyes
  • There are several different viewpoints about tanning, cancer and sunscreen products. I’m not going into all the details.
    • Dr. Phil Maffetone mentions specifically here that building a moderate tan is still a very important way to protect skin. 
    • When running in sunny conditions, use sunscreen on your exposed skin surfaces, in particular your face, shoulders, arms and legs.
    • I’d be careful about the type of sunscreen to use. There are many sunscreens on the marketing with chemicals that are very bad for you. There are several consumer reports online that review the best sunscreens. 

To sum things up

There are several things you can control when training and racing in hot and humid weather conditions. 

  • Adjust your pace according to effort level, don’t blindly follow a specific pace.
  • If you want to develop an aerobic base and train at low heart rate, it’s best not to increase your heart rate training zone on hot and humid days.
  • Instead of getting frustrated by weather conditions you can’t control, focus on what you can control. Having a positive mindset will help limit your stress levels, which is an important component of training as well. So the following for 
  • Training in hot and humid weather conditions:
    • Run early mornings or in the evenings
    • Split your long runs into 2 shorter runs
    • Run indoors on a treadmill for some or all of your workouts
    • Hydrate well
    • Run with an ice bandana or ice bottle
    • Also consider, adding some heat training to part of your training cycle
    • And of course my favorite, just slow down your pace.

When you slow down, you’re still getting a great workout in, even if your pace is significantly slower. This is great training for your mind as well, to learn to enjoy this process. Patience is absolutely key here. 

Marathon PR Training Program

If you enjoyed this video, check out my Marathon PR Training Program. This course includes 25 new videos (more than 5 hours of video footage) about low heart rate training, nutrition, race strategies and mind sets to improve your running. 

There are also flexible and editable training plans with different goals:

More info can be found at extramilest.com/marathon

I would love to hear from you!

What has worked well for you to deal with hot and humid weather conditions. Please let me know in the comments!

Have fun out there on your runs and stay cool my friends! Cheers.



Leave a Reply