Is it safe outside right now?
HeatCue turns temperature and humidity into one plain verdict for where you are. Built on wet bulb and WBGT, the numbers heat safety actually runs on.
DangerTime to find shade.
Heat isn’t just temperature.
Humidity keeps sweat from cooling you, so heat hits harder than the number says.
The same 31 degrees can be an easy afternoon or a dangerous one. Humidity decides, so HeatCue runs on wet bulb and WBGT instead of the plain forecast.
Learn the science →How it works
Two readings in, one verdict out
- 1
It reads the air
Live temperature and humidity for your area: an outdoor, in-shade estimate, as close as weather data allows.
- 2
It runs the science
A published method folds the two into WBGT, the measure sport and workplace heat guidance is written against.
- 3
You read one word
Safe, Caution, Danger, or Extreme, with a plain sentence on what to change. One second, and you know.
Safe
Good to be outside.
Sweat is cooling you the way it should.
Caution
Take water and breaks.
Sweat evaporates slower now, so you heat up faster.
Danger
Time to find shade.
Cooling down gets hard. Heat builds even at rest.
Extreme
Stay inside if you can.
Sweat barely evaporates. Your body cannot shed this heat for long.
See the heat coming.
Pro adds alerts before the heat, the 7-day outlook, more places, and profiles for kids, older adults, and dogs.
- The current verdict for your location: WBGT, wet bulb, and the risk band.
- The full Learn library and the heat calculator.
- Threshold alertsProA heads-up before it gets dangerous
- The 7-day heat outlookProPlan runs, hikes, and walks
- Home screen widgetsProThe verdict without opening the app
- Every place you care aboutProHome, the trailhead, grandma’s town
- At-risk and dog profilesProEach with its own heat limits
ProFeatures marked Pro come with HeatCue Pro. Pro is a subscription, with a one-time Permanent unlock if you prefer to pay once. Prices show on the App Store at launch.
Questions, answered
Is HeatCue free?
Yes. The heat verdict for your location is free, always: WBGT, wet bulb, and the risk band. HeatCue Pro adds threshold alerts, the 7-day outlook, home screen widgets, more places, and the at-risk and dog profiles.
What is wet bulb temperature?
The lowest temperature your sweat can cool you to. In dry air it sits far below the thermometer; in humid air the two converge and sweating stops working. Past a wet bulb of about 31 degrees Celsius (88 degrees Fahrenheit), heat builds in a resting body even in deep shade.
What is WBGT?
Wet bulb globe temperature: one number for how hard the heat is on your body, folding air temperature and humidity together with a published method. Sport and workplace heat guidance is written against WBGT, and it is the headline number in HeatCue.
Why can a mild forecast still be dangerous?
Humidity. When the air already holds plenty of water, sweat sits on your skin instead of evaporating, and you stop cooling. A humid 31 degrees Celsius is harder on your body than a dry 40. Wet bulb and WBGT see that; the plain forecast does not.
Where do the readings come from?
Public weather data for your area. Readings are outdoor, in-shade estimates. Direct sun adds heat the method does not see, so in open sun, act one band earlier.
Is HeatCue medical advice?
No. HeatCue shows conditions and general guidance drawn from published heat categories. It is an awareness tool, not medical advice. Anyone confused, fainting, or getting worse after cooling down needs emergency care.
Know before you go.
HeatCue is coming to iPhone in eleven languages. The verdict is free; Pro adds the foresight.