Learn
Heat, explained in plain language. Why one number beats the forecast, and what to do when it climbs.
Wet bulb temperature
The ceiling on what sweat can do, and the line behind the Limit band.
Wet bulb globe temperature
How the weather becomes one number, and where the lines are.
Signs of heat illness
What heat exhaustion and heat stroke look like, and what to do.
Staying safe, band by band
What to change at Caution, Danger, and Extreme.
Protecting others
Kids, older adults, dogs, and anyone pushing hard feel heat before you do.
The human heat limit
Where heat passes what a body can survive, and how we know.
Try it
Heat calculator
Try any temperature and humidity and see which band it lands in.