Extreme Heat: How We Measure it, and What it Means to You

Written By Dalton Behringer

Summer’s here, and with it comes a familiar but often overlooked threat to every job site, event, and weekend adventure: heat stress.

Traditional air-temperature or heat-index readings only tell part of the story. Humidity, solar radiation, and wind combine to shape how hot it really feels and how our bodies cope. That’s where Wet-Bulb Globe Temperature (WBGT) steps in.

What Is WBGT, and Why It Works

Unlike “feels-like” temperatures, WBGT is a scientifically validated metric used by the U.S. military, professional sports teams, and OSHA to set safe work/rest cycles and hydration guidelines. Where ambient air temperature is measured in the shade, and heat index blends air temp with humidity, WBGT also accounts for:

  • Radiant heat (direct sun exposure and cloud cover)

  • Evaporative cooling (the humidity component)

  • Air temperature (the ambient temp component)

That means two days at 90°F can feel dramatically different depending on dew point, cloud cover, and wind. WBGT captures that nuance so you know what conditions really feel like on the ground.

The SiteRisk Approach to Heat Risk

  1. Data Fusion
    We ingest WBGT forecasts from hundreds of weather models and produce a range of outcomes to gauge uncertainty.

  2. Scenario Simulation
    For each location, we run best-case, worst-case, and “official” forecast scenarios, so you see the full risk range.

  3. Risk Scoring
    Those WBGT values feed into a 0–100 Heat Risk Score, calibrated against how heat impacts human physiology (productivity, safety, and health).

  4. Personalized Alerts
    Lastly, our AI learns your specific risk tolerance, whether you’re scheduling construction crews, event staff, or weekend hikes, and translates that score into a simple, color-coded risk tier. (Basic risk tiers shown below)

Why This Matters

  • Avoid False Alarms: Ambient air temps or heat index can leave you under- or over-estimating real risk.

  • Act on the Right Cues: Get alerted exactly when conditions demand a break, extra hydration, or rescheduling, down to the hour.

  • Plan with Confidence: No more guesswork around cloud cover or wind effects - just clear, actionable guidance.

Basic risk levels associated with WBGT

Key WBGT Thresholds to Know

  • 85–87°F WBGT: Productivity for an acclimatized worker often drops to 50% (source)

  • ≈ 95°F WBGT: Near the theoretical limit of human heat tolerance - where the body cannot shed heat faster than it’s produced, even for healthy individuals (source)

WBGT isn’t just a niche tool for specialists; it’s the gold standard for real-world heat-risk management. At SiteRisk, we wrap this science into an AI-powered, location-specific score so you never have to guess whether conditions are safe.

Dalton Behringer