Dew point: —
| Distance | Cool conditions | Today’s air | Cost |
|---|
The table below is the calculator’s underlying model — the widely used temperature-plus-dew-point adjustment. Find the row closest to your conditions to see the typical pace cost and what it means at a 5:30/km (8:51/mile) training pace.
| Conditions (temp / dew point) | °F sum | Pace cost | At 5:30/km |
|---|---|---|---|
| 13°C / 7°C — cool, dry | ≤100 | 0% | 5:30 (no change) |
| 18°C / 12°C — mild | ~118 | ~1% | 5:33 |
| 21°C / 16°C — warm, humid | ~131 | ~2% | 5:37 |
| 24°C / 18°C — sticky | ~140 | ~3% | 5:40 |
| 27°C / 21°C — hot, humid | ~150 | ~4.5% | 5:45 |
| 30°C / 23°C — oppressive | ~160 | ~6% | 5:50 |
| 32°C / 26°C — extreme | ~170+ | 8–10%+ | 5:56–6:03 |
Worked example: at 24°C and 70% relative humidity the dew point is about 18°C, giving a heat cost of roughly 3%. A runner whose cool-weather half marathon pace is 5:30/km should plan around 5:40/km — about 3½ minutes slower across the 21.1km, from the air alone.
The calculator combines air temperature and dew point — the measure of how much moisture is already in the air, which determines how well your sweat can evaporate and cool you. The higher the combined value, the more blood your body diverts to your skin for cooling and the less is available to your working muscles, so the same pace costs more effort. The adjustment bands are based on the widely used temperature-plus-dew-point method from exercise physiology and coaching practice: no meaningful cost in cool, dry air, rising to 10% or more in genuinely oppressive conditions.
Treat the output as a planning guide, not a law. Individual heat tolerance varies with acclimatisation, body size, and fitness — two runners in the same air pay different taxes. The right use of this number is to set honest expectations before a warm run or race, so you pace by the day you actually got rather than the day you trained for. For the deeper story on why a slow, hot run doesn’t mean lost fitness, read Lost Fitness, or Just the Weather? and Cardiac Drift: Why Your Heart Rate Climbs on Easy Runs.
What dew point is bad for running? Below 13°C is comfortable; 16–18°C is noticeably harder; above 21°C evaporative cooling is severely limited and above 24°C conditions are oppressive for hard efforts.
Should I train by pace or effort in heat? Effort. Heat raises heart rate and perceived effort at any given pace, so holding cool-weather paces converts easy runs into hard ones. Let pace float; keep effort honest.
Does this apply to cycling? The physiology is the same but the cost is smaller — airflow at cycling speeds improves evaporative cooling, so riders typically pay roughly half the running penalty in the same air.
Planning a race-week menu too? Try the carb loading planner.
Kovr runs this calculation on every session — automatically.
Every run is stamped with the dew point and heat it happened in, weighed against your HRV and training load, and priced into your race predictions. No forms — just an honest read the moment your run syncs.
Download Kovr on the App Store