Training and racing in the heat is one of the toughest challenges a runner can face. When it's hot, your body has to send blood to your skin to cool you down at the same time as powering your muscles, so your heart works harder and any given pace feels tougher than it would in cooler weather.
While this does make things harder, it can be a great way to develop your fitness at the same time. With lots of races and marathons all over the world taking place in hot conditions, here are a list of simple but important tips to protect yourself whilst running in the heat.
Adapt Your Workout for the Conditions
Runna can now recommend adjusted pace targets when it's hot, so every session still delivers the same training benefit. If conditions are hot enough, you'll see an Adapt for Heat option on your workout.
Tap it to see the hourly forecast, pick when you're heading out, and get a recommendation tailored to those conditions.
Running slower in heat isn't slacking. Your body is working just as hard, and the training stimulus is actually the same. The adaptation keeps you on track without the guesswork.
How to Dress for Running in Hot Weather
By all means, you have the right to wear whatever you feel comfortable in, but it's worth bearing in mind that your body temperature will increase considerably when running in the heat. Running gear that felt manageable before you left the house might have you regretting your outfit choice 5 minutes into your run. If you enjoy wearing shorts, opt for those. If you're happy to wear a vest, go for it.
Another consideration is to be mindful about the fabric you choose when buying activewear. Bamboo is a popular choice at the moment and it's clear why. It's light, breathable, and sustainable. It can also protect your skin from UV rays!
Steer clear of 100% cotton, as it soaks up sweat and holds onto it, leaving you damp and weighed down. Go for a cotton-blend instead, which wicks sweat away far better.
Finally, colour matters too. It would be wise to avoid dark colours. White reflects more of the sun's light than black so you can stay cooler for longer!
Stay Hydrated
We hear it time and time again, but drinking enough water is SO important. Recommended daily intake varies between countries due to differing climates, but often, the advised amount to drink is around 2 litres to replace normal water loss (emphasis on normal).
When exerting more energy and sweating more, you should look to increase your water intake before, during and after you run.
If you're new to endurance running or running in the sun, buying yourself a hydration vest is a must (top tip: they are also great for carrying sugary snacks to keep you going). You can fill the water bottles up with your hydration drink of choice. We recommend adding electrolytes and salts to these too to replenish what your body is sweating out.
Slap on that SPF
Unprotected exposure to the sun's harmful ultraviolet (UV) rays can cause skin and eye damage, as well as suppression of the immune system, so remembering to lather on the suncream before heading outside for your long run is vital.
You could be outside for hours, so opt for a 50+ SPF to ensure maximum protection. Don't just put it on the areas that are exposed either. UV rays can penetrate some clothing so remember to rub it over your face, hands and body.
Avoid the Midday Heat
The sun is the strongest at midday. Avoid sunburn and dehydration by scheduling your run for early in the morning or once the sun has started setting. Taking a long run during the hottest part of the day can put a lot of strain on your body, which will not only affect your performance, but your recovery as well. In general, avoid running between 12pm and 3pm, and try to map out a shady route!
Embrace the Hat Hair
If you've ever experienced a sunburnt scalp, you most likely won't want to experience it again. Although there are more and more SPF products for your scalp becoming available, wearing a hat is a much easier, cheaper (not to mention less greasy!) option. A simple baseball cap or running hat will do the job.
If you're in the market for a running hat, try opting for one with breathable fabric. Covering your scalp when the sun is beating down on it will really help to prevent you from overheating when on your long runs, or risking heat stroke.
Use a Treadmill
If you have access to a gym, it could be an idea to hop on the treadmill to complete your more difficult workouts and prevent heat exhaustion. You can change the units of your plan to align with your treadmill, making the transition very simple.
What to Expect Out There
If you run with a smart watch that tracks your heart rate, don't let higher numbers alarm you. In warm and humid conditions, it's completely normal for your heart rate to run 10 to 20+ bpm higher than it would in cooler weather, even at exactly the same effort. This happens because your cardiovascular system is doing double duty: powering your muscles and working overtime to pump blood to your skin's surface to cool you down.
Remember that watches are also not 100% accurate when tracking heart rate.
Heart rate can also drift upward throughout a run in the heat, even if your pace stays the same. This is known as cardiac drift and it happens as rising body temperature and dehydration make your cardiovascular system work harder. It's a sign to pay attention to hydration and effort levels.
The bottom line: use heart rate as only one signal among many in hot weather, not as your sole guide. Effort, breathing, and how you feel overall will serve you much better on a sweltering day.
Run by Feel, Not by Numbers
Even with Runna's heat adaptation adjusting your paces, there will be days where you simply want to go by feel. That's where RPE, or Rate of Perceived Exertion, comes in.
Here's the principle: heat forces your body to divert blood to your skin to keep you cool, which means your heart and muscles have to work significantly harder to maintain the same speed.
A pace that felt comfortable at 12°C can feel brutal at 28°C, and that's not a sign you're unfit!
Rather than chasing a number on your watch, tune into how it feels:
Easy run? You should be able to hold a full conversation without gasping. If you can't, slow down regardless of pace.
Tempo or intervals? These will feel harder in the heat, and that's okay. Aim to match the effort level, not the split time.
A useful rule of thumb: slow your pace by roughly 15 to 30 seconds per kilometre for every 5°C above 15°C. So if your easy pace is normally 5:30/km and it's 30°C, running 6:00 to 6:15/km is smart training, not slacking.
Takeaways
Running in the heat is tough! Your body will be focusing on keeping you cool so your paces may not be as fast as you expect them to be. That's completely normal, and if you're using Runna's heat adaptation, your paces are already adjusted to reflect that.
Prepare accordingly and your training is likely to be unaffected. If you have to take your long run on a hot day, following the above steps will leave you in good stead. Be safe, be sensible and most importantly enjoy it!
If you're racing in a hot country, or there's a heatwave forecast for your race day, check out our guide below.