A Guide to Running in Hot & Humid Weather

As Australians we are no strangers to training in hot and humid conditions. While these conditions can be extra fatiguing and affect your day-to-day performance, you don't have to forgo your daily training due to rising temps, in fact you can utilise these conditions to maintain, and even improve, your aerobic performance. From being mindful of your water intake to adjusting your pace and the time of day you train, there are preventative measures you can take to ensure your safety and improve your conditioning when running in the heat.

When you exercise in the heat, your body works hard to keep its internal temperature stable. As your core temperature rises, blood vessels close to the skin widen and sweating increases in an effort to release heat through sweat evaporation. During moderate to high-intensity exercise, blood flow is prioritised to the working muscles, which reduces blood flow to the skin and limits the body’s ability to cool itself.

While heat can place significant strain on the body, repeated and controlled exposure to hot training conditions can lead to meaningful adaptations through a process known as heat acclimatisation. Over time, the body becomes more efficient at handling thermal stress, with cells responding more smoothly to rising temperatures rather than being “shocked” by the heat, which lowers the risk of heat-related illness. The brain also adapts, learning that heat is manageable, and improving its ability to regulate temperature and cope with discomfort, boosting mental resilience. Physically, heat acclimatisation increases sweat rate while conserving electrolytes, lowers heart rate, and expands blood plasma volume, allowing the heart to work more efficiently and helping the body remove heat more effectively.

To get the most from heat training while staying safe, it’s important to adjust your workouts appropriately. In hot or humid conditions, reducing your target effort to around 70–75% of your usual intensity allows the body to adapt without becoming overwhelmed. It can take a couple of weeks to acclimatise, so be patient, and make sure you prioritise recovery during this period. Gradual exposure, proper hydration, and paying attention to how your body feels are essential, with heat stress increased progressively over several sessions rather than all at once

Hydration is key before, during, and after your run—especially in hot weather when sweat loss increases. For runs over an hour, carry water using a handheld bottle, running belt, or hydration vest depending on distance and terrain. Drink when thirsty, but avoid overhydrating. Since sweating also flushes out electrolytes like sodium, potassium, and magnesium, it’s important to replace them—through sports drinks, electrolyte tablets, or salty snacks—to maintain performance, prevent cramps, and support overall health. Check out our comprehensive guide on hydration for runners for more details.

Sunscreen is a must, but reapply regularly. Cover up with a visor or wide-brimmed hat, UV-protective arm sleeves, and lightweight, breathable clothing in light colours. Sunglasses with a secure fit and ventilation or mesh panels in your clothing can help keep you cool. For longer runs, consider drape hats or hats with ice pockets to manage heat.

Avoid the peak sun between 10 a.m. and 4 p.m. by running early or late in the day. Temperatures and sun intensity are lower, making your run safer and more comfortable. In humid climates, mornings are often best since heat lingers after sunset. If running early in the morning doesn't come naturally to you, check out our tips on how to become a morning runner.

Running in heat feels harder, even at your usual pace. Reduce intensity to around 70–75% of your normal effort, keeping runs comfortable rather than race-ready. Focus on rhythm and accept slower paces as part of summer training. Monitor your breathing and heart rate, and take walk breaks if you feel overheated.

Choose shaded paths, trails, or routes near water to avoid direct sun. Avoid asphalt or concrete that absorbs heat, and consider indoor workouts during heatwaves, such as treadmill runs or HIIT sessions.

In hot conditions, sweat increases friction, so use anti-chafe sticks, moisture-wicking fabrics, and, for men, nipple guards. Protect your feet with breathable shoes, thin socks, and anti-blister products to stay comfortable and injury-free.

While it may be tempting to hop into an ice-cold shower after a hot run, your body will be better off gradually returning to its normal temperature, so avoid the polar plunge. You can use an ice cube on your pulse points (wrist and neck) to cool off and change out of your sweaty clothes. Hydrate and replenish lost fluid and electrolytes with a salty snack.

Running in hot conditions carries risks, and it’s important to recognise the signs of heat-related illness. Symptoms of heat exhaustion include dizziness, headache, nausea, weakness, and extreme thirst, while dehydration can also cause dry lips, irritability, and lightheadedness. If you notice any of these, stop running, move to a cool place, hydrate, and rest—do not push through. Heat exhaustion can escalate to heatstroke, a life-threatening condition where the body can no longer cool itself, causing confusion, disorientation, high body temperature, or even loss of consciousness. Seek immediate medical attention if heatstroke is suspected.