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Safety & HR · OSHA/NWS heat guidance

OSHA Heat Index & Risk Calculator

Estimate heat index from air temperature and humidity, then map the result to OSHA/NWS risk bands with worksite precautions.

Worksite Conditions

Use relative humidity directly or calculate it from dew point.

°F

Rothfusz regression range: 80°F to 130°F.

Humidity input
%

Enter a value from 1% to 100%.

Heat Risk Report

Calculated report is ready.

NOAA heat index

--°F

Awaiting inputs

Air temperature

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Relative humidity

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Risk band

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Work/rest guidance

Enter valid conditions to generate guidance.

Recommended precautions checklist

  • Enter valid conditions to generate a printable checklist.
Basis: NOAA heat index via the Rothfusz regression using air temperature in °F and relative humidity, mapped to OSHA/NWS heat risk bands for Safety & HR screening: below 91°F caution, 91°F to 103°F extreme caution, above 103°F to 115°F danger, and above 115°F extreme danger.
Self-tests not run

About the OSHA Heat Index & Risk Calculator

Safety managers, supervisors, and outdoor work crews use an OSHA heat index calculator to translate temperature and humidity into a practical heat-risk level. Enter jobsite conditions, sun exposure, workload, and acclimatization notes to support water, rest, shade, and monitoring decisions. It helps document a defensible heat stress plan before symptoms or emergencies develop.

How it works

  1. Enter the air temperature and relative humidity for the work area.
  2. Account for direct sun, protective clothing, workload, and worker acclimatization.
  3. Review the heat risk band and recommended protective actions.
  4. Plan water, rest, shade, supervision, and emergency response before work starts.

Frequently asked questions

What does the OSHA heat index measure?

Heat index combines air temperature and relative humidity to estimate how hot conditions feel to the body in shade. Direct sun, heavy work, protective clothing, and radiant heat can make actual jobsite risk higher.

Is heat index the same as wet bulb globe temperature?

No. Wet bulb globe temperature measures additional heat stress factors such as radiant heat and air movement, and is often better for detailed occupational heat assessment.

What should employers do when heat risk is high?

OSHA and NIOSH guidance emphasizes water, rest, shade, acclimatization, adjusted work intensity, symptom monitoring, and emergency procedures. The exact controls should match the task and worker risk.

Why does acclimatization matter?

Workers who are new, returning from absence, or starting a heat wave are at higher risk because the body has not adapted to heat stress. Gradual exposure and closer monitoring reduce that risk.

Does OSHA have a specific federal heat standard?

Federal OSHA uses the General Duty Clause and heat-related guidance while rulemaking and some state programs may impose more specific requirements. Employers should also check state OSHA plans.

References