How to Stay Cool While Running – Regardless of the Temperature

Summer running has its advantages, including more daylight hours and no snow or ice on the ground. However, the trade-off is hot temperatures and high humidity. But summer running does not need to be a suffer-fest! This article will guide you through evidence-based approaches for how to stay cool while running in summer heat and humidity. 

The effects of overheating while running

When you run, your body generates more metabolic heat than at rest, as a result of increased energy production. Your internal muscle and core temperatures elevate as your body dissipates the extra heat. To stay cool, your sweat rate increases. 

When you run in the heat and humidity, the external temperatures are higher. The high humidity makes sweating less effective, while the high heat changes your heat balance. In short, your body has a harder time dissipating metabolic heat when it also has to work to stay cool while running in a hot environment. 

Meanwhile, you sweat more when running in the heat. The sweat loss causes your blood plasma volume to decrease. If you do not replace fluids with water or sports drink, your heart rate will increase to compensate for the lower blood volume. Dehydration leads to performance declines – meaning you slow down and cannot run as far. 

Other physiological changes also occur when running in the heat, including changes in blood flow, neuromuscular feedback, lower aerobic capacity, and perception of effort. 

As a result, a temperature that may feel fine for walking outside feels harder for running – because it is actually physiologically harder. The increased thermoregulatory demands will make normal paces more challenging in the heat. You may notice your exercise tolerance lowering as you struggle to cover longer distances. 

Heat stress will lead to a decline in aerobic performance. If you try to push through or do not implement mitigation techniques, you risk exertional illness. Exertional heat illness occurs when the core temperature is too high; it can cause damage or death. Symptoms include very high heart and breathing rate, confusion or other altered mental state, nausea/vomiting, low blood pressure, dizziness, and headache. 

Tips for running in the heat

Given the performance declines and risk of running in the heat, you are likely how wondering how to stay cool while running in summer. There are multiple research-backed approaches for how to stay cool running in the heat – from hydration to gear to cooling techniques. 

Choose the right clothing and fabrics

Lighter color clothing reflects heat, while dark clothing retains heat. You will feel overheated if you run in the summer heat while wearing head-to-toe black gear. Instead, pick light-colored running tops, shorts, hats, and other gear to stay cool in summer. 

Likewise, your fabric impacts your body’s ability to cool. You want a fabric that wicks moisture away from your body. Skip any fabric that retains heat or moisture, such as the merino you may wear on winter runs. 

Stay hydrated

Hypohydration (a state of being in a fluid deficit, as a result of fluid loss without adequate replacement) will impair your running performance in the heat and humidity. Dehydration also increases your risk of exertional heat illness. Because you are sweating so much more when running in the heat, you need to hydrate more. 

Relying on water fountains is likely not sufficient for summer running. Instead, you want to carry your own water or sports drink using a hydration vest or handheld water bottle. Alternatively, you can set up an aid station and make small loops on your run so you can easily stop and drink.

Maintaining euhydration (fluid balance) in the heat begins with starting a run well-hydrated. If you start a run slightly dehydrated, it is very difficult to make that up during the run. Ensure you drink enough water and other fluids throughout the day to replace fluid loss from your previous run. Then, adapt your hydration strategy during runs, following the tips below.

How to stay hydrated during summer runs:

• Have 8-16 oz of water or electrolyte drink before you run. 
• Bring water on any length run – even if it’s <60 minutes – and sip to thirst.
• Runs >60 minutes, have a planned hydration strategy. Aim for 10-24 ounces per hour, based on your sweat rate and thirst. 
• Replace sodium as well, anywhere from 200mg to 700+ mg/hr based on your sweat composition. 

Related: How Much Water Should I Drink Before, During, and After Runs?

Time your runs wisely

Solar radiation will also impact overheating on a run. The time of day with highest sun also tends to be the hottest time of day. If you run in the middle of the day (10 AM to 2 PM), you will experience more heat stress. 

If lunchtime runs are your only option, try to opt for a shaded route. Otherwise, if you can, try to run early in the morning or later at the night, when the sun is less direct and temperatures are often cooler. 

Use cooling techniques

Want the secret to how to stay cool while running? Try using ice or cold water to cool your skin while running. These evidence-based cooling techniques involve ingesting cold fluids, using ice packs against the skin, or dousing the head, neck, and/or wrists with water. Pre-cooling techniques are used before you start running, while mid-cooling techniques are used during the run. 

A 2015 review in the British Journal of Sports Medicine found an overall effect of pre-cooling and mid-cooling to improve performance in the heat by 6.7%. An ice vest during running had the most significant effect of the cooling techniques, with a 21.5% improvement. A 2020 study in the International Journal of Environmental Research and Public Health similarly found that mid-cooling of the wrists resulted in lower RPE and faster running speeds when running in 80 degrees Fahrenheit (27 C).

How to use cooling techniques:

• Drink an icy cold beverage before you run
• Fill your hydration bottles or pack with ice 
• Put a reusable ice pack in the back of your hydration vest
• Tuck ice into your hat, light-colored cooling sleeves, or a bandana
• Wet and freeze a hat, cooling sleeves, or bandana before your run
• Douse your head, neck, and wrists with water during a run

What to wear while running in hot weather, by temperature

Overheating will impair performance at any temperature, whether in summer or winter. What you wear in any temperature will impact your body’s ability to regulate heat. Whether it’s 80 degrees or 30 degrees, you want to account for metabolic heat production when choosing what to wear. In most scenarios, that means dressing as if it’s 10-15 degrees warmer than the actual ambient temperature. 

(All temperatures are in Fahrenheit.)

40 degree weather

While unlikely, you could theoretically overheat in 40 degree weather if you overdress. 40 degree weather is above freezing, so you do not have to worry about impaired muscle function or frostbite like you could in 30 degree weather. If you bundle up as if you are running in sub-freezing temperatures, you could potentially overheat on a run in 40 degree weather. 

What you were in 40 degree weather will depend on sweat rate, work intensity, and individual preference. If you tend to overheat or are doing a hard workout, you may opt for shorts and a long-sleeved shirt. If you are a light sweater and doing an easy run, you might choose to wear a long-sleeved shirt and leggings. Gloves are optional, based on preference. 

50 degree weather

When running in 50 degree weather, you could overheat if you wear too many layers. Most runners feel more comfortable in shorts, since the leg muscles generate more metabolic heat when working. Depending on work intensity and preference, you may opt for a thin wicking long-sleeved shirt or a short-sleeved shirt. You likely will not need gloves or other layers. 

60 degree weather 

While 60 degree weather may feel pleasant to walk in, you may start to feel a bit warm when running. Most runners will want to wear a short sleeve or sleeveless shirt, especially if doing a long run or hard workout. 

Direct sun on your face can make you feel hotter. A breathable hat or visor and sunglasses will protect you from the sun while running in the heat. 

70 degree weather (or warmer)

Once you reach 70 degree weather, you are truly running in the heat. You will want to dress as light as possible! Pick light-colored clothing with thin, wicking materials. A thin short sleeve or sleeveless shirt paired with shorts is ideal. As with 60 degrees, you may feel more comfortable if you protect your face and eyes from the sun. 

Related: What to Wear for Running in the Cold

Bonus tips to run in hot weather

Hydration and cooling techniques are two of the most effective approaches for how to stay cool while running in the heat. Beyond that, the best tip for how to run in hot weather comes down to this simple piece of advice: slow down your runs!

Is it harder to run in the heat?

As discussed in the first section, your body has to work harder to thermoregulate when running in the heat. Dehydration will also impair endurance and speed. Your heart rate, breathing rate, and rate of perceived exertion (RPE) will all be higher at the same pace when running in the heat. 

Wondering how to stay cool while running in the heat – and how to make runs feel easier in the heat? Slow down! If you train by heart rate, aim to keep your runs in the targeted heart rate zone, no matter how slow you have to go. Plan on paces being 30-60 seconds per mile slower (or more). If you train by RPE or the talk test, go as slow as you need to be able to maintain the appropriate effort. 

If running in the heat still feels hard, you can take short walk breaks of 15-60 seconds. These walk breaks do not undo your fitness or make you less of a runner. However, they do help your body regulate effort and stay cool when running in the heat. 

Does running in the heat burn more calories?

If you do not slow down your runs, running in the heat will burn more carbohydrates – and therefore more calories. However, this is not a reason to push harder in summer runs. Instead, you want to adjust your paces to keep the same intensity on summer runs. (Read here for more tips on how to stay in zone 2 during your summer runs.) 

Is it better to run in the cold or heat?

In terms of absolute performance, you will run faster when running in cooler temperatures. If you are wondering how to run a marathon in the heat, you will have to accept that you will run slower than a marathon in 35 to 55 degree temperatures. 

In terms of training, running in the heat is difficult – but that does not mean you should avoid it. With the appropriate measures to stay cool, you can continue to train throughout the summer. As an added bonus, you may be faster when the cooler fall temperatures arrive! 

Running in the heat, recapped

Running in the heat will be harder. However, if you know how to stay cool while running, with approaches such as cooling techniques, hydration strategies, and slowing down, you can stay safe and enjoy summer running. 

Keep reading for more guidance on running in the heat:

• Heat Acclimation Strategies for Summer Races
• How to Best Adjust Your Training for Running in the Heat
• Tips for Racing in the Heat

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