Summer is one of the best times of year to run. Longer days, lighter evenings and plenty of opportunities to get outside make it easy to stay motivated. But when temperatures climb, your usual training can suddenly feel much harder than expected.
If you've ever wondered why your easy pace feels like marathon effort during a heatwave, you're not alone. Running in the heat places extra stress on your body, meaning your heart has to work harder, you lose more fluid through sweat and recovery can take longer too.
The good news? A few simple adjustments can help you stay safe, keep your training on track and even become a stronger runner over time.
Why does running feel so much harder in the heat?
When you run, your body naturally produces heat. On a cool day, it's easier to get rid of that excess heat, but in hot or humid conditions your body has to work much harder to keep your temperature under control.
To cool itself down, your body sends more blood to your skin and increases sweat production. That means your cardiovascular system is trying to do two jobs at once: supplying oxygen to your working muscles while helping you stay cool. As a result, your heart rate rises and maintaining your normal pace takes more effort.
That's why a run that usually feels comfortable can suddenly feel much tougher, even if your fitness hasn't changed.
Don't worry about pace, run by effort
One of the biggest mistakes runners make during hot weather is trying to stick to the same pace they would run in cooler conditions.
The reality is that slower doesn't mean less effective. Your body is already working harder, so trying to force your usual pace often leads to unnecessary fatigue and a longer recovery.
Instead, focus on how the run feels. Easy runs should still feel easy enough to hold a conversation, while harder sessions should match the intended effort rather than a specific number on your watch.
As a rough guide, many runners slow by around 15 to 30 seconds per kilometre for every 5°C above around 15°C. Think of it as adjusting to the conditions, not losing fitness.
Expect your heart rate to be higher
If you train with a heart rate monitor, don't be surprised if the numbers are higher than usual.
Hot weather often pushes heart rate up by 10 to 20 beats per minute, even when you're running at the same effort. As your body warms up and dehydration begins to set in, your heart has to work even harder to pump blood around your body. This gradual increase is known as cardiac drift.
Rather than chasing a heart rate or pace target, use those numbers alongside how you're feeling. Your breathing, effort level and overall comfort are often better indicators of whether you're running at the right intensity.
Hydration starts before you head out
By the time you feel thirsty, you're already beginning to dehydrate. That's why staying hydrated starts well before you lace up your shoes.
Try to drink regularly throughout the day before your run, particularly if you know you'll be training in hot conditions. During longer runs, carrying water or planning a route with refill points can make a big difference, especially if you're out for more than an hour.
After your run, continue replacing the fluids you've lost through sweat. If you've completed a long session or it's been especially hot, a drink containing electrolytes can help replace some of the salts lost alongside water.
Dress for the weather
What you wear can make a surprising difference to how comfortable your run feels.
Lightweight technical fabrics are designed to move sweat away from your skin, helping it evaporate more easily and keeping you cooler than cotton, which tends to hold onto moisture.
Choosing lighter-coloured clothing can also help by reflecting more sunlight, while a breathable running cap and sunglasses offer extra protection from direct sun. And don't forget sunscreen. Applying a high SPF before heading out can help protect your skin, even on cloudy days.
Choose the coolest part of the day
If possible, shift your runs to early morning or later in the evening when temperatures are lower and the sun is less intense.
Running in the middle of the day exposes you to stronger sunlight and often the hottest conditions, making every kilometre feel harder than it needs to. If you can't avoid daytime running, look for routes with plenty of shade and consider shortening your session if the heat becomes overwhelming.
Know when it's time to stop
Feeling a little slower is completely normal, but feeling unwell isn't.
If you experience dizziness, nausea, confusion, chills or a severe headache while running, stop immediately and move somewhere cool. Drink fluids if you can and seek medical attention if your symptoms don't improve. Heat exhaustion and heat stroke are serious conditions, so it's always better to cut a run short than try to push through.
Can running in the heat make you a better runner?
It might not feel like it during a sweltering long run, but training in warm conditions can have benefits.
Over time, your body becomes more efficient at cooling itself, starts sweating earlier and improves its ability to regulate temperature. These adaptations can make running in the heat feel more manageable and may even help improve performance when you return to cooler conditions.
The key is to build up gradually. Give yourself time to adapt, adjust your pace when needed and remember that consistency is far more important than forcing a particular split on a hot day.
After all, the best summer runs aren't always the fastest. They're the ones that leave you feeling strong enough to come back and do it again tomorrow.
