How to Handle Running in the Heat & Humidity
How to Handle Running in the Heat & Humidity
As the seasons change and we head into warmer, more humid months, many runners begin to notice a distinct shift in how their runs feel. What once felt smooth and steady in the cooler temperatures of winter and spring can suddenly feel like a struggle. This isn’t in your head—running in heat and humidity places real, physiological stress on your body.
Why Running Feels Harder in the Heat
As temperatures rise, so does your heart rate. Once the temperature hits 65–75°F, your heart rate can increase by 2 to 4 beats per minute. Go above 75°F, and that increase can jump to as much as 10 beats per minute. The same pace that felt easy just weeks ago will now require more effort.
Humidity adds another layer. When relative humidity climbs above 50%, your heart rate can spike by up to 10 beats per minute. Your body works overtime to regulate its core temperature, diverting blood away from your muscles and toward your skin to help cool you down. This means your muscles (and brain) receive less oxygenated blood, making you feel more fatigued and mentally foggy.
Despite how hard it feels, you’re not losing fitness—your body is simply working harder to adapt.
The Benefits of Training in Tough Conditions
The good news? Training in heat and humidity can actually improve your performance in the long run. Exposure to high temperatures increases your plasma volume and hemoglobin levels, which improves oxygen delivery to your muscles. Once the weather cools down in the fall, you may find yourself running faster and feeling stronger.
However, consistent exposure to extreme heat can also impair your aerobic performance, decreasing VO₂ max and aerobic power. That’s why it’s essential to train smart—not just hard.
Why You Should Train by Effort, Not Pace
During summer running, forget the watch and tune into your body. Heat causes your heart rate to rise while stroke volume (the amount of blood pumped with each beat) decreases. So even though your heart is working harder, it’s pumping out less. Your body also burns more carbohydrates to fuel itself, leading to faster energy depletion.
Instead of focusing on numerical pace, focus on your effort. Let your body guide your training intensity and know that slowing down is both normal and necessary.
Tips for Running in the Heat and Humidity
You can’t change the weather, but you can prepare for it. Here are some tips to help make your summer runs more bearable—and even enjoyable:
- 🧊 Run with ice in your hat, or freeze your hat the night before a long run or race
- ❄️ Use a cold, wet, or frozen towel or buff on your neck or head
- 🎒 Place soft ice packs in your hydration vest to cool your back
- 💧 Drink cold water before your run to “cool from the inside out”
- 🧃 Soft-freeze your hydration bottles/vest bladder
- 👙 Ice in your sports bra during a race (yes, it helps!)
- ✋ Hold melting ice in your hand—helps reduce perceived discomfort
- 🕶️ Wear sunglasses to avoid squinting, which can signal stress to your brain
- 😤 Don’t hold back the swearing—studies show cursing can boost pain tolerance by up to 33%!
- 🧠 Shift your mindset from “this is hard” to “I get to do this”
- 🎯 Focus on effort, not pace
Acclimating to the Heat
It takes about two weeks of consistent exposure to heat and humidity for your body to fully acclimate. During this time, prioritize easy runs and limit high-intensity workouts. If you need a break, running indoors on a treadmill can still help maintain heat adaptations.
Remember, high humidity also affects your body’s ability to sweat efficiently. Sweat doesn’t evaporate as quickly, leading to a higher core temperature and a greater risk of dehydration.
Stay Hydrated and Stay Safe
Hydration is more critical than ever. You’re losing more fluids through sweat, so your baseline hydration needs increase. Start every run well-hydrated and replenish fluids throughout the day—not just during or after your workout.
Listen to your body. If you experience dizziness, nausea, lightheadedness, confusion, vomiting, or a high heart rate, stop running immediately. These are warning signs that your body is under serious stress and needs rest and rehydration.
Final Thought:
Summer running is tough—but it’s also a chance to build strength, mental resilience, and long-term fitness. Embrace the season by adjusting your expectations, training smart, and staying cool (literally and figuratively). Come fall, you’ll be glad you did.
Weekend Mileage (6.21.25) – Head Over Heels Training says:
[…] in learning why summer running feels harder or its benefits, you can read my recent blog post: How to Handle Running in the Heat & Humidity, which can be found on the website. You can also find some tips/reminders that may help make it a […]