Hot weather changes the workout.
Heat and humidity make a normal pace cost more. This calculator gives a conservative pace adjustment so the training effort stays closer to the plan.
Estimate a hot-weather pace
Enter your normal target pace plus the expected temperature, humidity, and workout duration. Use the result as a starting point, then run by effort.
The goal is not to protect the original split. The goal is to preserve the intended effort and recover well enough for the next run.
Humidity matters because sweat cools you less effectively when the air is already saturated.
For hard workouts, consider moving earlier, shortening reps, extending recovery, or using a treadmill when conditions are unsafe.
El Helou et al. (2012) analyzed major marathon results and found environmental parameters, especially temperature, meaningfully affect marathon performance.
View sourcePeriard et al. (2015) published consensus recommendations on preparing for and competing in hot conditions, including acclimation and heat-management strategies.
View sourceHow much slower in heat?
See the research behind hot-weather pace adjustments.
Check readiness signals
Weather is one signal; recovery is another.
Plans for real life
See how Treadly adjusts when the day does not match the spreadsheet.
How coaching decisions work
Treadly explains why the plan changed.
Is this a race prediction calculator?
No. It is a training-effort guide. Racing in heat depends on fitness, acclimation, sun exposure, wind, fluids, course, and how you tolerate heat.
Should I run by pace or effort in heat?
Use pace as a starting estimate, then prioritize effort, breathing, and safety. A hot-weather easy run should still feel easy.
Can Treadly adjust workouts for heat?
Treadly is built around the idea that the plan should respond to weather, recovery, and real life instead of pretending every day is identical.
A calculator is useful. A plan that adjusts is better.
Treadly brings these signals into your actual running plan, then explains why the workout changed.