NWS Heat Index Calculator
Apply the National Weather Service heat-index procedure to supplied temperature and humidity.
Your result
EVERYDAYEnter your values and select calculate.
On this page How it works & practical examples
How to use the NWS Heat Index Calculator
Apply the National Weather Service heat-index procedure to supplied temperature and humidity. The result represents shaded conditions and light wind rather than full-sun exposure.
The calculation
Worked example
90°F and 70% relative humidity yield a heat index of about 105.922°F using the adjusted NWS procedure.
Assumptions and limits
No forecast or personal risk classification. Heat exposure can be dangerous outside or beyond the approximation’s domain; sun, clothing, exertion and individual factors are excluded.
Common questions
Which inputs should I use?
Apply the National Weather Service heat-index procedure to supplied temperature and humidity. The result represents shaded conditions and light wind rather than full-sun exposure.
What does the result exclude?
No forecast or personal risk classification. Heat exposure can be dangerous outside or beyond the approximation’s domain; sun, clothing, exertion and individual factors are excluded.