Heat Stress Heatmap Calculator

How to use

1. Enter your site conditions and worker assumptions.
2. Pick a model that matches your reporting needs.
3. Set ranges to generate a temperature-humidity heatmap.
4. Review the risk band and guidance shown above.
5. Export CSV or PDF for audits and ESG notes.

Formula used

Example data table

Why heat stress mapping matters for ESG risk

Heat exposure can disrupt productivity, raise incident risk, and increase heat related downtime. Mapping conditions across temperature and humidity helps quantify climate vulnerability at assets and worksites. The grid supports scenario testing, such as a 2°C warming increment or a seasonal humidity shift, and highlights hours when controls are required. A repeatable method improves comparability across sites and supports risk registers and adaptation plans.

Inputs that shape the heatmap

The heatmap combines air temperature and relative humidity, then adds optional drivers that often vary by microclimate. Solar radiation typically ranges from 0 to 1000 W/m², while wind commonly spans 0 to 10 m/s. Sun exposure represents shading and ground heating effects. Activity load and clothing insulation act as screening modifiers, because heavy work and layered PPE reduce heat dissipation. Use measured or forecast inputs and document sources.

Interpreting WBGT and Heat Index outputs

Two output modes are provided. Heat Index summarizes perceived heat from temperature and humidity and is useful for public communication. WBGT estimate integrates wet bulb temperature with an approximated globe temperature, reflecting solar load and wind. Screening bands are shown as Low, Moderate, High, and Extreme. In many programs, 25–28°C suggests caution, 28–31°C signals strong controls, and above 31°C needs strict limits.

Operational controls linked to risk bands

Translate bands into clear actions. Low conditions focus on hydration access and symptom awareness. Moderate conditions benefit from shaded recovery areas, buddy checks, and task rotation. High conditions often require planned work rest cycles, pre cooling, electrolyte guidance, and enhanced supervision. Extreme conditions should prioritize engineering controls, schedule changes, or stopping non essential tasks. Consider vulnerable groups and acclimatization status, plus heat stored in roofs and pavements.

Documenting decisions for audits and disclosures

Exports support governance and compliance workflows. CSV files can populate dashboards, while PDF snapshots provide a fixed record for incident reviews and management sign off. Store inputs, assumptions, and the selected model alongside controls implemented. Track indicators such as days in High or Extreme bands, and link them to outcomes including near misses, absenteeism, and energy use for cooling. Consistent metrics strengthen disclosures and supplier engagement.

FAQs

What does the heatmap represent?

Each cell shows the estimated heat stress metric for a temperature and humidity pair, plus a risk band. It helps you see how small shifts in conditions can move a site into higher control requirements.

How do WBGT estimate and Heat Index differ?

Heat Index uses temperature and humidity to express perceived heat. WBGT estimate also reflects solar load and wind through wet bulb and globe components, so it is better for outdoor work planning and exposure management.

What if I do not know solar radiation?

Use 0 W/m² for night or fully shaded areas. For daytime sun, a practical screening value is 600–900 W/m². Document the assumption and rerun the scenario when measured data becomes available.

How are clothing and activity handled?

Activity load and clothing insulation add a small conservative adjustment to the final score. This supports planning when workers perform heavy tasks or wear layered PPE that reduces evaporative cooling.

Can this be used indoors?

Yes, for screening. Set solar near 0 and use the measured air speed. For radiant sources such as furnaces, the globe approximation may understate risk, so confirm with site measurements if decisions are critical.

How should I use the exports in reporting?

Save the CSV for dashboards and the PDF for sign off records. Store inputs, assumptions, and controls with each export, then track days in High or Extreme bands as a comparable indicator across assets and suppliers.