Last updated: March 2, 2026 by James Wilson

Heat Index Calculator

Formula

Uses the Rothfusz regression: HI = -42.379 + 2.049T + 10.143RH - 0.2248TRH - 0.00684T² - 0.0548RH² + ...
(T in °F, RH in %).

Calculate the NWS heat index using the Rothfusz regression equation. The heat index combines temperature and humidity to reflect how hot it actually feels to the human body.

Common use cases:

  • Heat stroke prevention
  • Outdoor event safety planning
  • Athletic training guidelines

Frequently Asked Questions

JW

James Wilson

Licensed Professional Engineer, PE, MS Civil Engineering

James is a Licensed Professional Engineer with a Master's in Civil Engineering and over 12 years of experience in structural design and construction project management. He specializes in building calculations, material estimation, and physics-based engineering tools.

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