How to Adjust Run Pace in the Heat

With this simple formula.

Running in the heat and humidity can be brutal. I know because I live in Florida.

Last weekend, we did a 12-mile trail run in 90°F. My husband, Matt, described the experience as “feeling like a piece of meat roasting inside a sous vide bag.”

Not pleasant.

But alas, we have chosen to live in the Sunshine State and along with the sea breezes and palm trees, we must accept the mind-numbing heat and gasp-inducing humidity.

Your ability to run in the heat depends on a few different factors: your physical fitness, how much you sweat, your level of heat acclimation, and most importantly the weather.

How much does heat and humidity affect your pace?

Luckily, Matt is a self-described “weather nerd,” so we’ll explain.

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First, let’s review some meteorological terms and discover what they mean for runners:

• Temperature- Indicates how hot or cold the air is. Temperature also directly affects how much moisture the air can hold: warm air can hold more moisture than cold air. For runners, temperature plays a big role in both comfort and performance. When it’s hot, your body tries to cool itself off by producing sweat. As the sweat evaporates, it takes excess body heat with it, which cools you off.

• Humidity: Humidity is the concentration of water vapor in the air. High humidity makes it feel hotter than the actual temperature might suggest. Because there’s already water vapor in the air, your sweat doesn’t evaporate as easily, which makes it harder to cool off. For runners, high humidity places extra strain on the body and can make an easy run feel hard.

• Dew Point: (This one is important) The dew point is the temperature at which air becomes fully saturated with moisture (100% relative humidity). This causes water vapor to condense into liquid. Think about dew on grass or fog on the road. A higher dew point indicates that there’s moisture in the air. Running in a dew point above 60°F (15.5°C) starts to feel uncomfortable, and when it’s above 70°F (21°C), it can feel oppressive.

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Formulas to adjust running pace

Now you know how temperature, humidity, and dew point can affect how a run feels, but how can you use that information to your advantage?

Formula #1: Find your heat-adjusted pace.

Here’s an easy formula you can use to adjust your running pace in the heat.

Base Pace (min/mile) + [(Dew Point°F - 60) x 0.025] = Adjusted Pace (min/mile)

• Base pace- is your typical running pace in ideal conditions.

• Dew point- in degrees Fahrenheit.

• 60- Running performance will be affected above this dew point threshold.

• 0.025: Additional minutes per mile to add for each degree the dew point exceeds 60°F.

For example, let’s say your base pace is 9:00 minutes per mile and the dew point is 70°F.

9:00 + [(70−60)×0.025] = 9:25 minutes per mile.

So you can see how dramatically dew point can affect your pace. But this formula doesn’t take into account temperature, which is something else to consider.

If you’re really a numbers person and want to dig a bit deeper, Coach Mark Hadley has a unique method of combining both temperature and dew point to make pace adjustments.

Formula #2: Add temperature to dew point and adjust your pace based on the total.

Temperature°F + Dew Point°F = total used to adjust running pace.

For example, let’s say the temperature is 90°F and the dew point is 70°F.

90 + 70 = 160

These are Coach Hadley’s recommendations:

• 100 or less: no pace adjustment

• 101 to 110: 0% to 0.5% pace adjustment

• 111 to 120: 0.5% to 1.0% pace adjustment

• 121 to 130: 1.0% to 2.0% pace adjustment

• 131 to 140: 2.0% to 3.0% pace adjustment

• 141 to 150: 3.0% to 4.5% pace adjustment

• 151 to 160: 4.5% to 6.0% pace adjustment

• 161 to 170: 6.0% to 8.0% pace adjustment

• 171 to 180: 8.0% to 10.0% pace adjustment

• Above 180: hard running not recommended

So with this example, we’re looking at a 4.5%-6% pace adjustment.

If you go with a middle value of 5%, this is how to adjust your pace.

• 7:00 min/mile: 5% slower = 7:21 min/mile

• 7:30 min/mile: 5% slower = 7:52 min/mile

• 8:00 min/mile: 5% slower = 8:24 min/mile

• 8:30 min/mile: 5% slower = 8:55 min/mile

• 9:00 min/mile: 5% slower = 9:27 min/mile

• 9:30 min/mile: 5% slower = 9:58 min/mile

• 10:00 min/mile: 5% slower = 10:30 min/mile

• 10:30 min/mile: 5% slower = 11:01 pace min/mile

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Tips for Running in the Heat

It’s one thing to know how weather conditions might affect your ability to run, but it’s another thing to know what to do about it. Sure, you can slow down, but there are plenty of other tools you should have in your Hot Runner Arsenal.

Hot Runner Arsenal Tools:

1. Wear the right clothing- For me, the least amount of clothing is best, because I sweat A LOT. But Florida is very sunny, so if you’re running around half-naked, be sure to wear sunscreen, a hat, and sunglasses. Zealios is our favorite sunscreen. Also, select moisture-wicking, lightweight clothing. Rabbit has a great perforated tank that’s made out of recycled coffee grounds (no joke) so it dries quickly, controls odor, and keeps you cool.

2. Pick the best time of day- Generally, if you run early in the morning, you have to contend with more humidity, but the temperature won’t be as high. If you run later in the afternoon, the humidity will be lower, but it will be hotter. Pick what works best for you and your physiology. If you download The Weather Channel app, you can view the best times of the day to run.

3. Know your sweat rate- (Planning a future post on this) It’s important to know how much fluid and electrolytes you lose per hour so you can decide how to fuel during a workout and what you need to take in post-workout. A simple way to calculate sweat rate is to weigh yourself (without clothing) before a run. Then, run for an hour and track your fluid intake. Finally, weigh yourself after the run (without clothing) and calculate the net loss. You don’t have to replace everything you lose, but you should replace a good portion. I like using my Hdrop hydration tracker for runs and bike rides.

   Stay Salty: Reusable Tech for the Seriously Sweaty Athlete

4. Run loops with DIY aid stations- This is a favorite trick of ours. Let’s say we have an 8-mile run. We put a cooler with ice and our bottles of hydration somewhere on a 2-mile loop. Then, every few miles, we stop to get a drink and grab some ice to stuff in our clothes. This is approximately the same distance between aid stations during an Ironman-branded race, so it makes for good practice.

5. Use ice to your advantage- Ice is your best friend, both in training and during a race. The skin on your face, hands, and feet is glabrous, meaning “without hair,” which makes it excellent for cooling purposes. At every aid station, I stick ice in my sports bra and grab a piece to hold while I’m running. The key is to switch back and forth from one hand to the other, so you don’t inhibit the cooling effect by making your skin too cold. The Huberman Lab podcast explains this phenomenon in great detail. If you read my post about the Cool Mitt technology out of Stanford, this is the same principle.

6. Carry your hydration- One downside to aid stations, both DIY and in a race, is that athletes often tend to chug liquid (me) once they get there, because they’ve had nothing to drink for a few miles. If your stomach is compromised due to heat or exertion, this doesn’t end well. Whereas, if you carry your hydration with you, it’s easy to sip whenever you feel the need. Also, it spaces out the consumption of fluid and carbs so there’s less risk of stomach upset. I don’t like carrying a handheld bottle, because it messes with your form. For training, I use either a Nathan hydration vest for long runs, and I race with my Naked Running Band. I used it at Ironman Florida last year. Matt likes his Salomon hydration vest and Orange Mud bottle quiver. (Amazon partner)

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I hope this provides you with a few tips for running in the heat, as well as an idea for how to adjust your running pace. I’m not a big numbers person (words are more my thing) so it rarely follow a formula.

However, I do take a look at temperature and humidity before I run just so I have a more realistic assessment of how my pace might be affected. This helps to prevent frustration when your speed drops off and your heart rate goes up. The more you run in the heat, the better it tends to get, but honestly, running in the summer is just rough, so be smart out there.

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