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Running in humidity can be even more difficult than running in the heat, and it’s actually the combination of the two both being high that really makes running super tough.


When assessing the risk of heat illnesses like heat exhaustion and heat stroke, humidity often plays a more significant role in the “real feel” temperature and the resultant risk.

Humidity makes running in hot temperatures even more intense on the body because when the moisture content of the air is higher, it feels hotter.

For example, when it’s 31° C out with 40% humidity, it will feel like 31° C, when it’s 31° C with 70% humidity, it will feel like 38° C.

When we bump up to 85% humidity at the same temperature, the Heat jumps to 43° C.


When we step outside our air-conditioned home to go for a run on a hot summer day with high humidity, it can feel like stepping into an intense tropical rainforest.

Even just walking around outside in weather like that can make us feel hot and sweaty in a matter of minutes.

When we run, the core temperature of our body naturally rises. In response, our body signals our sweat glands to produce sweat droplets.

The purpose of sweating is to reduce our core temperature by carrying excess heat to the surface of the skin through sweat. The evaporation process helps cool the body by releasing heat energy.

However, when we are running in humidity, the moisture content in the air prevents sweat from evaporating normally. As a result, the heat energy stays trapped in our body without getting released.

Running in humidity causes heat to build up in our body, increasing the risk of heat illnesses like heat exhaustion and heat stroke.

The risk of heat exhaustion when running on hot and humid days is escalated if we become too dehydrated.

The more dehydrated we become, the more our blood plasma level drops. The body responds by going into “survival mode.”

When our blood plasma level drops because we have not taken in enough fluids while running, blood flow to the surface of the skin decreases significantly because the body must conserve the available blood volume.

Instead, blood flow is focused on the essential organs to keep us alive rather than spread around to the surface of the skin to cool us down or to the GI tract for digestion.

This is the reason why many runners feel nauseous after consuming energy gels or sports drinks when running in the heat and humidity, digestion slows significantly when we run, but even more so as we become dehydrated.

This leaves the energy gel or carbohydrate-rich sport drink, and even water to some extent, to sit and slosh around in our stomach.

The key to preventing this is staying on top of our hydration from the beginning of our workout, making sure we’re taking fluid and electrolytes every 20-30 minutes on pace with our sweating.


The higher our core body temperature rises, the faster our heart will beat in order to try to keep up with the demands of our workout and supply enough oxygen and nutrients to our working muscles.

Our breathing rate will increase because the lungs need to take in more oxygen to fuel the overworking heart and muscles.

Dehydration worsen the cardiovascular challenge of running in humidity and heat because as our blood plasma level drops, we have less volume of blood.

Less blood is pumped to the muscles and tissues of the body per heartbeat.

In order to keep up with the muscles’ demand for oxygen and nutrients and to compensate for this reduced volume, the heart has to beat faster so that more blood is delivered.

Most runners will experience a heat rate increase of about 10-20 beats per minute when running in 32° C compared to running when it is 23° C.

This increase will be even more severe when running in humidity above 50%.

Also, an often-forgotten factor that makes it even more difficult to run on steamy, hot, humid days is that our brain is adversely affected as our core temperature rises.

After our core temperature rises high enough, our brain temperature also increases.

This can affect our focus, concentration, decision-making skills, and energy. We also start to feel dizzy, disoriented, and uncoordinated with our running form.


Unfortunately, no runner has the power to control intense humidity and heat, and other intense weather conditions, so it will challenging when we will have to run on hot and humid days.

1. Allow Your Body Time To Acclimate

According to some research, it takes about 10-14 days for our body to acclimate to super-hot weather and humidity runs.

We should be patient with ourself and adjust our workouts, as needed, while our body is adjusting to the added stress of running in the heat and humidity.

2. Run By Effort Not By Pace

Summer running, or days when it feels like an oven outside, we should focus on how our body feels, using effort and not pace to guide our workout.

Running in high humidity heat, we are less likely to hit specific paces in the heat. When we run by feel, we listen to our body, honouring its needs while still getting a quality workout.

3. Don’t Assume Running In The Afternoon Is Safe

Running in the early morning before the sun rises may help us avoid intense humidity heat.

Running in the evening is also a good recommendation, because the heat of the sun and the humidity will be lower.

4. Hydrate Enough Before And During And After Your Run

Staying well hydrated is crucial to prevent the dehydration that contributes to heat exhaustion when running in the heat and humidity.

Depending on our sweat rate and the environmental conditions, we should drink at least 120-250ml of water, electrolytes, and/or electrolyte-infused sports drink every 20-30 minutes during our run. And to make sure we rehydrate well with good electrolytes post-run.

5. Run In The Shade

Although it won’t take away the humidity, if it’s hot and sunny, running in the shade can help support our run.

Also, Trails are a great option for summer kilometres because they are usually shaded in more sections, from the natural canopy of the trees.

6. Wear Visor And Sunglasses

It’s also a good idea to wear a visor and running sunglasses to keep the sun off our face and out of our eyes while still permitting heat to escape from the top of our head.

7. Shift Your Training Schedule And Adjust Your Goals

If our training schedule calls for a long run or a hard workout during a heat wave or dreadfully humid day, we should focus on listening to our body, and run a distance that we can tolerate without feeling sick. And focusing on fast pace and sprints in high humidity and heat can also cause extreme fatigue, no breathing and extreme dehydration.

8. Soak Yourself With Water

When it’s super humid, the water won’t evaporate, but cool water can lower our body temperature.

If our run takes us past a safe body of water we’re allowed to enter, we should jump in before or halfway through our run to lower our body temperature. We will feel much better.

9. Run Indoors

Running indoors in an air conditioned space with a treadmill is also a good type of training whenever the heat index is considered at an elevated risk for developing heat exhaustion.

Even if the treadmill is not our favourite, it will avoid cancelling our run.

Running In High-Humidity And Heat Will Affect Our Body, Focus On Comfortable Runs And Pace, Good Hydration, Enjoy Some No High-Intensity Runs!


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