The short answer
A dew point running chart grades how sticky the air is. Below 10°C (50°F) is comfortable; 10–15°C (50–59°F) is noticeable; 15–18°C (59–64°F) is sticky; 18–21°C (64–70°F) is hard on any fast run; 21°C (70°F) and above is oppressive. Dew point beats relative humidity because it measures the moisture itself.
Key takeaways
- The dew point measures how much moisture the air holds; relative humidity changes with temperature.
- Below 10°C (50°F), humidity barely affects your pace.
- From 18°C (64°F), slow hard efforts by several per cent, more on hot days.
- Hadley's rule: add air °F to dew point °F; above 130, slow down 2% or more.
On this page
- What is the dew point, and why do runners use it?
- Dew point running chart in °C and °F
- Why is dew point better than relative humidity for runners?
- How do you use temperature plus dew point to adjust your pace?
- Where do you find the dew point for your run?
- What dew points do real race days bring?
- Questions runners ask
- Sources and method
Words this guide uses
- Dew point
- The temperature to which air must cool to become saturated; it rises with the amount of water vapour in the air.
- Relative humidity
- How close the air is to saturation at its current temperature, as a percentage.
- Pace-timed forecast
- The weather for each stretch of your route at the time you will actually run it.
What is the dew point, and why do runners use it?
The dew point is the temperature at which the air would be saturated with water vapour. Runners use it because it measures the moisture that stops sweat evaporating, and that moisture decides how hard a warm run feels.
You cool yourself mainly by evaporating sweat. The more water vapour already in the air, the slower that happens. A high dew point means sweat drips off you instead of carrying heat away. It is the core number in running in heat and humidity.
The dew point running chart below is in both units. To see the dew point along your own route, hour by hour at your pace, use the free tool Map your run.
Dew point running chart in °C and °F
Every whole degree from 0°C to 26°C (32°F to 78.8°F), with RunFast's band.
| Dew point (°C) | Dew point (°F) | How it feels on a run |
|---|---|---|
| 0 | 32.0 | Comfortable |
| 1 | 33.8 | Comfortable |
| 2 | 35.6 | Comfortable |
| 3 | 37.4 | Comfortable |
| 4 | 39.2 | Comfortable |
| 5 | 41.0 | Comfortable |
| 6 | 42.8 | Comfortable |
| 7 | 44.6 | Comfortable |
| 8 | 46.4 | Comfortable |
| 9 | 48.2 | Comfortable |
| 10 | 50.0 | Noticeable |
| 11 | 51.8 | Noticeable |
| 12 | 53.6 | Noticeable |
| 13 | 55.4 | Noticeable |
| 14 | 57.2 | Noticeable |
| 15 | 59.0 | Sticky |
| 16 | 60.8 | Sticky |
| 17 | 62.6 | Sticky |
| 18 | 64.4 | Hard |
| 19 | 66.2 | Hard |
| 20 | 68.0 | Hard |
| 21 | 69.8 | Oppressive |
| 22 | 71.6 | Oppressive |
| 23 | 73.4 | Oppressive |
| 24 | 75.2 | Oppressive |
| 25 | 77.0 | Oppressive |
| 26 | 78.8 | Oppressive |
Reading in Fahrenheit? Here is the same scale every 5°F, next to the US National Weather Service's summer comfort bands.
| Dew point (°F) | Dew point (°C) | National Weather Service | RunFast band |
|---|---|---|---|
| 40 | 4.4 | Dry and comfortable | Comfortable |
| 45 | 7.2 | Dry and comfortable | Comfortable |
| 50 | 10.0 | Dry and comfortable | Noticeable |
| 55 | 12.8 | Dry and comfortable | Noticeable |
| 60 | 15.6 | Sticky, muggy evenings | Sticky |
| 65 | 18.3 | Oppressive | Hard |
| 70 | 21.1 | Oppressive | Oppressive |
| 75 | 23.9 | Oppressive | Oppressive |
The runner's bands are a step stricter than the forecaster's. A runner at race pace makes far more heat than someone walking to the shops, so moisture starts to matter sooner.
Why is dew point better than relative humidity for runners?
Because relative humidity depends on the temperature, while the dew point doesn't. The same 70% humidity can be pleasant or brutal.
The National Weather Service gives the classic example: 30°F (−1°C) at 100% humidity feels much drier than 80°F (27°C) at 50%. The table shows the same effect for runners, at a constant 70% relative humidity.
| Air (°C) | Air (°F) | Dew point at 70% humidity (°C) | Dew point at 70% humidity (°F) | Band |
|---|---|---|---|---|
| 10 | 50 | 4.8 | 40.6 | Comfortable |
| 20 | 68 | 14.4 | 57.8 | Noticeable |
| 25 | 77 | 19.1 | 66.4 | Hard |
| 30 | 86 | 23.9 | 75.0 | Oppressive |
How do you use temperature plus dew point to adjust your pace?
Add the air temperature in °F to the dew point in °F, then look up the sum in coach Mark Hadley's chart. It is a rule of thumb from 2013, not a peer-reviewed model, but runners have used it for years.
| Sum (°F + °F) | Slow your pace by (%) |
|---|---|
| 100 or less | 0 |
| 101–110 | 0–0.5 |
| 111–120 | 0.5–1 |
| 121–130 | 1–2 |
| 131–140 | 2–3 |
| 141–150 | 3–4.5 |
| 151–160 | 4.5–6 |
| 161–170 | 6–8 |
| 171–180 | 8–10 |
| Above 180 | Hard running not recommended |
Take a 5:30 per km (8:51 per mile) tempo run at 25°C (77°F). With a 10°C (50°F) dew point the sum is 127, so slow to 5:33–5:37 per km (8:56–9:02 per mile). With an 18°C (64°F) dew point the sum is 141: slow to 5:40–5:45 per km (9:07–9:15 per mile). Hadley suggests half the adjustment for interval repeats.
For other methods, see heat-adjusted pace calculators compared.
Where do you find the dew point for your run?
In your weather app's hourly details, for the hour and place you'll be running. Most apps list it near the humidity, including Apple Weather.
Read the hour of your run, not the day's high. A pace-timed forecast, the weather for each stretch at the time you'll run it, matters most on long runs, when two or three hours can bring a sea breeze or the midday sun.
What dew points do real race days bring?
Most big-city race days stay below the sticky band. At Boston, London and Berlin, 26 of the 27 race days from 2015 to 2024 kept a four-hour runner below a 15°C (59°F) dew point. These are the highest dew points along each course for a four-hour finish, from RunFast's analysis of ERA5 reanalysis (reanalysis, not a thermometer at the start line).
| Race day | Peak dew point (°C) | Peak dew point (°F) | Band |
|---|---|---|---|
| Boston Marathon, USA, 18 April 2022 | −2.2 | 28.0 | Comfortable |
| Berlin Marathon, Germany, 29 September 2024 | 6.2 | 43.2 | Comfortable |
| London Marathon, UK, 22 April 2018 | 13.6 | 56.5 | Noticeable |
| Berlin Marathon, Germany, 26 September 2021 | 14.9 | 58.8 | Noticeable |
| Boston Marathon, USA, 11 October 2021 | 15.7 | 60.3 | Sticky |
| Comrades Marathon, South Africa, 28 August 2022 (nine-hour finish) | 15.9 | 60.6 | Sticky |
The Met Office calls London 2018 the warmest London Marathon on record, at 24.2°C (75.6°F) in St James's Park. Yet its dew point stayed in the noticeable band. Its heat came more from the sun and temperature. You can replay any of these days on the London race page or the Boston race page. For what to aim for, see what is a good dew point for running.
Questions runners ask
What dew point do forecasters call muggy?
The US National Weather Service office in La Crosse, Wisconsin, describes a summer dew point of 55°F (13°C) or below as dry and comfortable. From 55°F to 65°F (13–18°C) the air becomes sticky, with muggy evenings. At 65°F (18°C) and above there is a lot of moisture in the air and it becomes oppressive. Runners feel each step sooner, because they make so much heat.
Can the dew point ever be higher than the air temperature?
No. The dew point can rise to the air temperature but not above it. When the two are equal, relative humidity is 100% and you get fog, mist or dew. A small gap between them on a warm morning is a warning sign for runners: there is little room left for sweat to evaporate, so expect the run to feel harder than the temperature suggests.
How do you convert a dew point from Celsius to Fahrenheit?
Multiply by 9, divide by 5 and add 32, exactly as for air temperature. A dew point of 18°C is 64.4°F, and 21°C is 69.8°F. To go the other way, subtract 32, multiply by 5 and divide by 9: 65°F is 18.3°C. The chart in this guide lists every whole degree from 0°C to 26°C (32°F to 78.8°F).
Is a 60°F dew point bad for running?
It is noticeable rather than bad. A 60°F dew point is 15.6°C, at the bottom of the sticky band. On a 77°F (25°C) day, Hadley's sum is 137, which his chart turns into a 2–3% slower pace for continuous running. On a 65°F (18°C) morning the sum is 125, so 1–2%. Easy runs need no plan beyond running by feel.
Does a high dew point matter on a cool morning?
Very little. The dew point can't exceed the air temperature, so a 12°C (54°F) morning can have a dew point of 12°C at most. Hadley's sum is then about 107, which his chart treats as a 0–0.5% adjustment. Heat stress needs both heat and moisture. A high dew point on a cool day mostly means damp kit and misty air.
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
- Met Office (2025). London Marathon 2025: weather, records and event milestones
- Copernicus Climate Change Service (ECMWF) (2026). ERA5 hourly data on single levels from 1940 to present
The chart's °F values are exact conversions (°F = °C × 9/5 + 32). The 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); the US National Weather Service bands are quoted from its La Crosse office. Dew points for a given temperature and relative humidity use the Magnus formula, as in RunFast's engine. Pace adjustments use Mark Hadley's published temperature plus dew point chart (sums of °F values, rounded to whole degrees), applied to the paces shown. Race-day dew points are the highest along each course for a four-hour marathon finish (nine hours at Comrades), from RunFast's analysis of ERA5 reanalysis (Copernicus Climate Change Service), hourly: reanalysis, not a thermometer at the start line.
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.