Running in the Heat Calculator

This tool is for informational purposes only and is not medical advice. Always consult a healthcare provider before starting new exercise routines, especially in extreme heat.

How Adjusted Pace Is Calculated

Adjusted pace represents the slower speed required to run safely in hot weather. First, the calculator uses the temperature and humidity to determine the Heat Index, which measures how hot it actually feels outside. Next, it identifies a base slowdown time based on the severity of the heat. Finally, it fine-tunes this number by adding extra time for factors like low fitness, lack of acclimatization, or age.

1. Calculate the "feels like" temperature using Heat Index algorithms.
2. Apply a base time penalty per mile based on the heat intensity.
3. Increase the penalty for personal risk factors like medication use or age.

What Your Adjusted Pace Means

Your adjusted pace provides an estimate of how much to slow down to maintain performance without risking your health. Following this target provides information to help manage your body core temperature and avoid dangerous conditions.

Comfortable Conditions: If the heat index is below 80°F, your pace will likely remain close to normal. You can proceed with your standard training plan without major changes.

Caution Zone: When the heat index reaches 90°F, the calculator often adds 30-60 seconds per mile. One may consider strictly run at this slower speed to prevent early fatigue and dehydration.

Danger Zone: If the heat index exceeds 105°F, your adjusted pace will be significantly slower. In these conditions, strictly follow the recommended pace, reduce your distance, or consider moving your workout indoors.

To ensure reliability, check the weather right before you head out, as conditions can change quickly.