Hygrometer
iPhone · iOS 17 or later
Humidity, and what it actually means.
A round analog dial reads the outdoor humidity where you are. Underneath it sits everything a single percentage leaves out: the dew point, how much water the air is really carrying, and how much margin is left before it starts condensing.
The bands on the dial are not invented. Their boundaries follow the ASHRAE 55 comfort envelope and the EPA and WHO guidance on damp buildings: 30–50% is the healthy range, and sustained readings above 60% are where mould and dust mites take hold.
The number behind the number
80% humidity can be drier than 40%.
Relative humidity is a ratio, not an amount — it says how close the air is to full, and warm air can hold far more. So the same percentage means completely different things at different temperatures. Hygrometer shows you the amount as well.
80%
relative humidity at 0°C
3.9 g/m³ water in the air
40%
relative humidity at 25°C
9.2 g/m³ water in the air
Dew point
The temperature the air would have to cool to before it starts giving up water. It barely moves over a day, which is why it beats humidity as a comfort measure.
Water in air
Absolute humidity in grams per cubic metre — the amount the percentage hides.
Mixing ratio
Grams of water per kilogram of dry air. Unchanged as a parcel of air warms or expands, which is why forecasters use it.
Condensation margin
How far the air is from saturation, stated as a temperature: anything colder than the dew point collects water.
Ahead of you
A day of humidity, drawn the way it behaves.
Humidity runs inverse to temperature: the air keeps its water while the night cools and the percentage climbs. The 24-hour chart draws the comfortable band behind the curve so you read the shape against the range that matters, and calls out the hour it peaks. Swipe across for the hourly and 10-day forecast.
Home & Rooms
Track every room. Get alerted before mould starts.
Connect your HomeKit temperature and humidity sensors or log room readings. Hygrometer watches your living room, bedroom, basement, or greenhouse, evaluates sustained moisture against the EPA and WHO 60% thresholds, and alerts you before mould spores can grow.
Locations
Save and compare places worldwide.
Keep track of multiple outdoor locations. Check whether your weekend destination is dry or sticky, or monitor family abroad with live local weather conditions and dew point readouts.
Widgets
Mostly, you never open it.
Home Screen widgets in three sizes and Lock Screen widgets in three shapes. They render the reading the app has already cached and step through the stored hourly forecast, so they do no network work of their own.
Where the numbers come from
Outdoor readings come from Apple Weather, which reports weather conditions from nearby meteorological stations and atmospheric models.
Your iPhone has no built-in humidity sensor; for indoor rooms, Hygrometer integrates directly with your Apple HomeKit temperature and humidity accessories or accepts manual logs.
- Requires
- iPhone, iOS 17 or later
- Price
- Free
- Outdoor readings
- Apple Weather
- Indoor support
- Apple HomeKit sensors
- Units
- °C and °F
- Appearance
- Light, dark or system
- Languages
- 8
- Data collected
- None