The short answer
A good dew point for running is below 10°C (50°F), where humidity barely touches your pace. Up to about 13°C (55°F) still feels comfortable. From 15°C (59°F) the air turns sticky, from 18°C (64°F) hard efforts suffer, and from 21°C (70°F) it is oppressive. The warmer the day, the more each degree of dew point costs.
Key takeaways
- Below 10°C (50°F) dew point, run your normal paces.
- From 18°C (64°F), slow every hard effort; from 21°C (70°F), keep runs easy.
- A low dew point on a hot, sunny day can still mean High heat stress.
- The harder and longer the run, the more a high dew point costs.
On this page
Words this guide uses
- Dew point
- The temperature at which the air would be saturated; a direct measure of how much moisture it holds.
- WBGT
- Wet bulb globe temperature, the heat-stress index that combines air temperature, humidity, sun and wind.
- Pace-timed forecast
- The weather for each stretch of your route at the time you will actually run it.
What is a good dew point for running?
Below 10°C (50°F) is a good dew point for running: the air is dry enough that humidity barely affects your pace. Up to about 13°C (55°F) still feels fine to most runners, and from 18°C (64°F) every hard effort suffers.
The dew point measures the moisture in the air, which is what stops sweat evaporating. It is the humidity number that matters for running in heat and humidity, and the full degree-by-degree conversion is in our dew point running chart.
| RunFast band | Dew point (°C) | Dew point (°F) | National Weather Service | On a warm day |
|---|---|---|---|---|
| Comfortable | Below 10 | Below 50 | Dry and comfortable | Run normal paces |
| Noticeable | 10–15 | 50–59 | Comfortable up to 55°F (13°C), then sticky | Hard efforts feel a little harder |
| Sticky | 15–18 | 59–64 | Sticky, muggy evenings | Slow hard efforts by a few per cent |
| Hard | 18–21 | 64–70 | Oppressive from 65°F (18°C) | Slow every hard effort; shorten long runs |
| Oppressive | 21 and above | 70 and above | Oppressive | Keep runs easy and short |
Want to know the dew point for your own run? Map your run shows it for every kilometre of your route at the time you'll be there.
Does a good dew point depend on the air temperature?
Yes. The same dew point costs more on a hot day, because heat and moisture add up. That is the idea behind coach Mark Hadley's rule: add the air temperature in °F to the dew point in °F.
Take a dew point of 12°C (53.6°F), in the noticeable band, and change only the air.
| Air, °C (°F) | Hadley sum | Hadley pace adjustment (%) | WBGT in sun, °C (°F) | WBGT under cloud, °C (°F) |
|---|---|---|---|---|
| 15 (59) | 113 | 0.5–1 | 17.9 (64.2), Low | 13.4 (56.1), Low |
| 22 (71.6) | 125 | 1–2 | 21.6 (70.9), Moderate | 17.4 (63.3), Low |
| 30 (86) | 140 | 2–3 | 25.7 (78.3), High | 21.7 (71.0), Moderate |
So a "good" dew point is only half the answer. At 30°C (86°F), even a dry 10°C (50°F) dew point gives a WBGT of 25.1°C (77.2°F) in strong sun, in the High band. The sun counts as much as the humidity.
Is the same dew point fine for an easy run and a race?
No. The harder and longer you run, the more heat you make and the more the dew point matters. An easy 5 km (3.1 miles) in sticky air is fine for most; a marathon at goal pace is not.
Hadley suggests half his continuous-run adjustment for interval repeats, since you cool in the recoveries. John Davis notes heat hurts shorter races less than the marathon, because in a 5 km you can outrun your thermal limits.
Set your bar by the session:
- Easy runs: run by feel in any band below oppressive.
- Tempo runs and long runs: slow down from the sticky band.
- Races of 10 km (6.2 miles) and up: plan a slower pace from the noticeable band if the day is also warm.
What dew points do runners meet on race day?
Often moderate dew points with high heat stress, because sun and temperature do the damage. The Comrades Marathon in South Africa, about 90 km (56 miles) from Durban to Pietermaritzburg or back, shows it year after year.
These are the peaks along the course for a nine-hour finisher, from RunFast's analysis of ERA5 reanalysis (reanalysis, not a thermometer at the start line). There was no race in 2020 or 2021, and 2022 was run on 28 August.
| Comrades race day | Peak dew point, °C (°F) | Warmest air, °C (°F) | Peak WBGT, °C (°F) |
|---|---|---|---|
| 31 May 2015 (up run) | 15.3 (59.5) | 25.6 (78.1) | 26.9 (80.4), High |
| 29 May 2016 (down run) | 13.5 (56.3) | 26.1 (79.0) | 23.0 (73.4), High |
| 4 June 2017 (up run) | 12.3 (54.1) | 26.4 (79.5) | 25.0 (77.0), High |
| 10 June 2018 (down run) | 15.1 (59.2) | 21.2 (70.2) | 20.5 (68.9), Moderate |
| 9 June 2019 (up run) | 14.5 (58.1) | 22.4 (72.3) | 19.4 (66.9), Moderate |
| 28 August 2022 (down run) | 15.9 (60.6) | 23.0 (73.4) | 22.2 (72.0), Moderate |
| 11 June 2023 (down run) | 14.3 (57.7) | 22.0 (71.6) | 22.2 (72.0), Moderate |
| 9 June 2024 (up run) | 9.6 (49.3) | 20.8 (69.4) | 20.1 (68.2), Moderate |
In 2017 the dew point was in the noticeable band, yet heat stress reached High. Compare a cool northern race: the 2024 Berlin Marathon in Germany peaked at a 6.2°C (43.2°F) dew point and a WBGT of 14.0°C (57.2°F) for a four-hour runner. Replay any of these days on the Comrades race page.
What should you do when the dew point is too high?
Slow down, shorten the session, or move it. The dew point usually changes far less through the day than the temperature, so running at dawn cools the air but rarely dries it.
- Slow the pace before you start, using Hadley's chart or a heat-adjusted pace calculator.
- Seek shade and moving air: tree-lined paths, the waterfront, a breezier route.
- Swap a hard session for an easy one when the dew point is oppressive.
- Use the treadmill with a fan if heat stress is High or Extreme.
On race day, follow the official flags. The American College of Sports Medicine's 2007 position stand advises runners at increased risk to slow down at moderate heat stress and to withdraw at high. Medical advice overrides anything in this guide, which is not medical advice. For why humidity is better read as dew point, see does humidity affect running pace.
Questions runners ask
Is a dew point of 10°C good for running?
Yes. A 10°C (50°F) dew point sits at the top of comfortable and the bottom of noticeable. On a 20°C (68°F) day, Hadley's temperature plus dew point sum is 118, which his chart turns into a 0.5–1% slower pace for continuous running. Most runners won't notice it on an easy run. Watch the temperature and the sun instead.
Is a 70°F dew point too high to run?
It is too high for hard running for most people, but not for an easy run if you're careful. A 70°F (21.1°C) dew point is oppressive. With 80°F (26.7°C) air, Hadley's sum is 150, which calls for 3–4.5% slower continuous running. Keep it short, run by effort, drink, and stop if you feel dizzy. Race flags and medical advice come first.
Does the dew point change during a long run?
It can, especially over several hours or a big change of place. At the 2016 Comrades Marathon in South Africa, a down run from Pietermaritzburg to the coast at Durban, ERA5 reanalysis gives a peak dew point of 13.5°C (56.3°F) for a nine-hour finisher. An eleven-hour finisher, nearer Durban later in the day, met 15.2°C (59.4°F), in the sticky band.
Should I use the dew point or the heat index for running?
The dew point with the air temperature, if you can. John Davis, who built the Running Writings heat calculator, notes that the heat index was derived from people at rest. Its baked-in assumptions may not hold during running, so pace adjustments from it are less accurate. Temperature plus dew point, or plus relative humidity, gives the same answer and lets the marathon data speak.
Is a dew point below freezing good for running?
For humidity, yes: the air is very dry and sweat evaporates easily. The 2022 Boston Marathon had a peak dew point of about −2.5°C (27.5°F) for a three-hour runner, by ERA5 reanalysis, with air of 9–12°C (48–54°F). At that point the temperature matters more than the moisture. El Helou and colleagues found marathon speeds peak at air temperatures of about 4–10°C (39–50°F).
See the heat at your pace.
Drop in your route (GPX, FIT or TCX), pick the day and your pace, and see the feels like, dew point and heat stress for every kilometre, timed to when you’ll be there. Free, in your browser, no sign-up.
Sources and method
- US National Weather Service, La Crosse (2026). Why dew point vs humidity
- Maximum Performance Running (Mark Hadley) (2013). Temperature + dew point for pace adjustments
- Running Writings (John Davis) (2026). Heat and humidity pace calculator for runners
- PLOS ONE (2012). Impact of environmental parameters on marathon running performance (El Helou et al.)
- Medicine & Science in Sports & Exercise (ACSM) (2007). American College of Sports Medicine position stand: exertional heat illness during training and competition (Armstrong et al.)
- Copernicus Climate Change Service (ECMWF) (2026). ERA5 hourly data on single levels from 1940 to present
Bands are the ones RunFast's engine uses (comfortable below 10°C, noticeable 10–15°C, sticky 15–18°C, hard 18–21°C, oppressive 21°C and above), shown next to the US National Weather Service's La Crosse bands. Pace adjustments use Mark Hadley's published temperature plus dew point chart (sums of °F values, rounded to whole degrees). WBGT values are from RunFast's engine, which follows Liljegren et al. (2008), with wind 10 km/h (6 mph) at 10 m, sea level, and either strong sun (600 W/m² at a sun height of 45°) or full cloud. Heat-stress levels follow the ACSM 2007 WBGT categories as RunFast grades them (Low below 18.3°C, Moderate to 22.8°C, High to 27.8°C, Extreme above). Comrades figures are the highest values along the course for a nine-hour finish, from RunFast's analysis of ERA5 reanalysis (Copernicus Climate Change Service), hourly: reanalysis, not a thermometer at the start line. Comrades was not run in 2020 or 2021, and the 2022 race was held on 28 August. Imperial values are our conversions.
Wes Thomson
Wes Thomson builds RunFast, which times the heat, humidity and dew point to a runner's own pace along the route, and its sister Windline, live wind forecasts for cyclists. Both run on the same forecast engine. He writes these guides with one focus: what the weather will do to your run, kilometre by kilometre, and how to plan around it.