Heat & Humidity Adjuster — Run · Angela Naeth Coaching

How to use this calculator

This running calculator is designed to help you adjust your pacing when training or racing in conditions that may be warmer and/or more humid than you are accustomed to. It adjusts your target running wattage, pace and/or heart rate based on how different the conditions are compared to what you've acclimated for.

1. Enter a target running wattage, pace, and/or HR into the respective input fields. You may enter one, two, or all three metrics — the calculator will adjust whichever you've provided.

2. Select approximately how much warmer the conditions will be than you're accustomed to. Example: if you've been training in 60°F conditions and today it's 75°F, select 15.

3. Select approximately how much more humid it will be than you're accustomed to. Example: if you've been training in 50% humidity and today it's 75%, select 20+.

The calculator estimates how much performance will be degraded and adjusts the target metric(s) accordingly. Results update live as you type.

Your Targets & Conditions

Target Wattage

Running watts (Stryd) — optional

Target Pace

Format: mm:ss per mile — optional

Target Heart Rate

bpm — optional

Warmer Than Accustomed

Select delta vs. your usual training temp

More Humid Than Accustomed

Select delta vs. your usual training humidity

Adjusted Targets

Enter at least one target (wattage, pace, or HR) above to see your heat- and humidity-adjusted values here.

Why this matters: Heat and humidity raise cardiac strain while lowering sustainable power and pace — your heart rate will climb at the same effort while your output drops. Using adjusted targets keeps your session at the intended physiological intensity, protecting adaptation and reducing risk of overcooking a key workout or race.