Heat & Humidity Pace Adjuster
Enter your goal pace plus expected race-day temperature and humidity to see a more realistic, heat-adjusted pace. Most published marathon course records are set around 10-12°C (50-54°F) with low humidity -- warmer or muggier than that, and effort-matched pace typically slows. Southeast Asia's races routinely start well above that baseline, so this exists to set an honest goal instead of a cool-weather one.
Enter your goal pace, then the conditions you expect on race day.
min
sec
Enter a goal pace, temperature, and humidity to see your heat-adjusted pace.
Racing somewhere hot and humid? Pair this with the race fueling calculator to plan hydration and sodium too, and browse races across Southeast Asia.
Frequently asked questions
Does heat really slow down running pace?
Yes -- your body diverts blood flow to the skin to cool itself, leaving less for working muscles, and heart rate climbs at the same effort. Above roughly 12-15°C (54-59°F), most runners lose measurable pace as temperature and humidity rise, even at an easy effort.
What temperature is ideal for marathon racing?
Most elite marathon course records are set around 10-12°C (50-54°F) with low humidity. That's the reference point this calculator adjusts from -- warmer or more humid than that, and pace typically has to give a little to hold the same effort.
Does humidity matter more than temperature?
Above about 20°C (68°F), yes, disproportionately -- high humidity blocks sweat evaporation, your body's main cooling method, so a hot, humid day punishes pace far more than an equally hot, dry one. This is exactly the combination common across much of Southeast Asia.
How should I adjust my race-day goal for hot weather?
Treat your heat-adjusted pace as the more realistic target, not your cool-weather PB pace. Start conservatively, lean on effort and heart rate over GPS pace, and prioritize hydration and finishing well over chasing a time that was set for different conditions.