Free pace calculator
Running pace targets for heat and humidity
The pace you planned can feel harder once the air warms. Enter the temperature, dew point (or humidity), and your pace in cool air for a prospective pace target from RunWeather's shared model. It is an estimate of the weather effect, not a measurement of your effort.
Your run
Aim for
9:27 /mi
+0:27 /mi
The same effort as your cool-air pace, in these conditions. Let the pace fall there and keep the effort where it belongs. Heat strain is real at this level: drink before you go and watch for heart rate drift.
Assumptions: 60 minutes, no wind, and the selected sky. All effort options use the ordinary training heat curve, including Race. This estimate has no personal heat-response or acclimatisation adjustment.
Model estimate, not a measured same-effort pace or a safety clearance.
Heat and humidity pace chart
Model-estimated change per mile from a 9:00 per mile (5:36 per km) baseline, with Easy selected, 60 minutes, no wind, and shade or overcast sky. These are calculator assumptions. The calculator above lets you change the baseline, effort and sky.
| Air temp | Dew 45°F7°C | Dew 50°F10°C | Dew 55°F13°C | Dew 60°F16°C | Dew 65°F18°C | Dew 70°F21°C | Dew 75°F24°C |
|---|---|---|---|---|---|---|---|
| 60°F16°C | 0:00 | +0:05 | +0:05 | +0:05 | |||
| 65°F18°C | +0:05 | +0:05 | +0:05 | +0:11 | +0:16 | ||
| 70°F21°C | +0:05 | +0:11 | +0:11 | +0:16 | +0:22 | +0:22 | |
| 75°F24°C | +0:11 | +0:11 | +0:11 | +0:16 | +0:22 | +0:27 | +0:43 (unsafe heat) |
| 80°F27°C | +0:11 | +0:16 | +0:16 | +0:22 | +0:27 | +0:32 | +0:49 (unsafe heat) |
| 85°F29°C | +0:16 | +0:16 | +0:22 | +0:27 | +0:32 | +0:38 | +0:49 (unsafe heat) |
| 90°F32°C | +0:22 | +0:22 | +0:22 | +0:27 | +0:32 | +0:38 | +0:54 (unsafe heat) |
| 95°F35°C | +0:22 | +0:27 | +0:27 | +0:32 | +0:38 | +0:43 (unsafe heat) | +0:54 (unsafe heat) |
Red: the shared model flags unsafe heat. Blank: the dew point cannot be higher than the air temperature. Every pace number is calculated by RunWeather's shared engine. Model estimates, not measured runs.
Same temperature, different dew point
Both examples below have 80°F (27°C) air and the same 9:00 per mile baseline. Only dew point and the selected effort change. Read the numbers as the shape of this model, not a stopwatch promise.
| Dew point | Easy target | Race effort target |
|---|---|---|
| 50°F (10°C) | 9:16 /mi5:45 /km | 9:16 /mi5:45 /km |
| 72°F (22°C) | 9:38 /mi5:59 /km | 9:43 /mi6:02 /km |
Model estimates for 60 minutes, no wind and shade or overcast. Race changes the effort setting within the ordinary training heat curve. It does not select the separate race-planning curve or predict a finish time.
Pace target and weather-adjusted pace
A pace target looks forward: you supply a baseline and the calculator estimates a target for the weather you entered. Weather-adjusted pace looks back at a completed run and estimates its equivalent in neutral conditions. Neither is a fitness test, and this calculator does not turn an estimate into a race prediction.
Method and source limits
The calculator calls the same core package as the app. It estimates wet-bulb globe temperature from the weather inputs, then applies the shared pace model. Sky selection is a cloud-cover proxy for sun, rather than a measured radiation reading. The fixed duration and absent wind describe this scenario, not every run.
A controlled running study by Che Muhamed and colleagues found greater heat strain as humidity increased at the same temperature. That supports including moisture; it does not supply a fixed pace change for you. Research on weather and endurance race performance also describes population associations, rather than validating these individual training targets.
The IOC consensus on sport in the heat notes that equal WBGT need not produce equal strain in different athletes. This calculator has no personal heat-response fit, and its current model does not soften pace for acclimatisation. The exact steps in the chart come from model choices. They are not dew-point thresholds where everyone's physiology changes.
For training context, read the heat and humidity pace adjustment guide and why dew point matters for running. The Run Score method explains how the shared engine combines weather and safety warnings, and Heat Risk Today compares modelled heat stress by city.
The dew point chart gives moisture context in Celsius and Fahrenheit. This calculator assumes no wind; read running in wind for the separate effect of route direction and exposure.
Running in heat and humidity: FAQ
How much should I slow down running in the heat?
There is no fixed seconds-per-mile answer for every runner. Enter your baseline pace and conditions to get a model estimate, then check it against your actual effort. The chart and examples show the output of this model, not measured responses or a promise about your run.
Why does this calculator ask for dew point instead of temperature alone?
At the same air temperature, a higher dew point means more moisture in the air. Controlled running research found greater heat strain as humidity rose at a fixed temperature. The calculator combines temperature and dew point rather than treating one dew point as a physiological threshold.
Can I use relative humidity instead of dew point?
Yes. Switch the moisture field to humidity. The shared core converts relative humidity and air temperature into dew point, so both input modes feed the same pace calculation. The dew point cannot be higher than the air temperature.
Does the slower pace mean I am losing fitness?
This calculator does not measure fitness. It changes the baseline pace you supply using a weather model, without your run history or a personal heat-response fit. A slower estimate is not evidence that your fitness has changed, and it cannot explain every difficult run.
Where do these numbers come from?
The calculator calls RunWeather's shared core pace model with a 60-minute duration, no wind and the selected sky. All effort options, including Race, use its ordinary training heat curve. It has no personal heat-response or acclimatisation adjustment. The exact pace coefficients are model choices, not a validated prediction for each runner.
When is it too hot to run at all?
When estimated heat stress reaches the unsafe tier, the calculator flags it in red, and so does the chart. The pace is an estimate and does not make the run safe. Move the run to a cooler hour or a suitably cooler indoor setting.
Get this on every run, automatically
RunWeather syncs with Strava, plans your week, and learns your heat tolerance, so the right time to run finds you. Free on iPhone and Android.
Running weather guides
How each kind of weather changes your run, and the cities where it matters most.