Heat-Adjusted Pace
Estimate how much hotter weather slows your running pace, with an approximate percentage to add by temperature.
| Temperature | Add to pace | A 9:00/mi run becomes | Notes |
|---|---|---|---|
| 60°F / 16°C | — | 9:00/mi | Ideal — little to no adjustment |
| 65°F / 18°C | +1.5% | 9:08/mi | Slightly warm |
| 70°F / 21°C | +3% | 9:16/mi | Noticeable on longer efforts |
| 75°F / 24°C | +5% | 9:27/mi | Ease back, especially with humidity |
| 80°F / 27°C | +7% | 9:38/mi | Hot — run by effort, not pace |
| 85°F / 29°C | +9% | 9:49/mi | Hot + humid compounds quickly |
| 90°F / 32°C | +12% | 10:05/mi | Very hot — consider rescheduling hard work |
| 95°F / 35°C | +16% | 10:26/mi | Extreme — easy effort only |
Approximate, vs an ideal ~60°F/16°C day. Humidity and direct sun make hot days harder still — run by effort.
Heat makes a given pace cost more effort, because your body diverts blood to the skin to cool down. The chart shows an approximate percentage to add to your time as temperature climbs above an ideal of about 60°F (16°C). These are estimates — humidity and direct sun make hot days harder still.
The practical rule on hot days is to run by effort, not pace: hold your normal easy or tempo feel and accept a slower pace. To apply the adjustment, work out your goal pace on the main calculator, then add the percentage from the table for the day's conditions.
Frequently asked questions
How much does heat slow running pace?
Roughly 1–3% slower around 70°F, rising to 7–12% or more above 85–90°F, and worse with high humidity. The chart lists an approximate add-on by temperature.
Does humidity matter as much as temperature?
Yes — high humidity stops sweat evaporating, which is how you shed heat, so a humid 80°F day can feel harder than a dry 90°F one. Treat the chart as a dry-air baseline and add more when it's muggy.
Should I adjust my goal time for a hot race?
For an honest target, yes. Many runners set a slightly slower goal or simply race by effort in the heat, then push the last stretch if they feel good.