Humidity Sensors in Mobile Apps
A practical guide to the rare on-device humidity sensor — how to read it on supported Android phones and how to fall back to weather APIs everywhere else.
Founder, Newly
A handful of Android devices ship with a relative humidity sensor — the original Galaxy S4, Note 4, a few ASUS phones, and a small number of rugged industrial devices. iPhones have never included one. This guide shows you what to do when it's present, and how to ship a humidity feature anyway.
Key Takeaways
- Android exposes humidity (where present) via `Sensor.TYPE_RELATIVE_HUMIDITY`. iOS has no equivalent.
- Always feature-detect — the sensor is missing on more than 95% of devices.
- For broad reach, use a weather API + GPS to compute outdoor humidity instead.
- Indoor humidity from the on-device sensor often reads several % off the user's wall-mounted hygrometer; treat it as an estimate.
Humidity Sensor at a Glance
What It Is & How It Works
What it is. A capacitive humidity sensor measures the dielectric constant of a polymer film, which varies with absorbed water vapour. The OS exposes the result as relative humidity in percent.
How it works. On Android, register a listener for `TYPE_RELATIVE_HUMIDITY`. On iOS and on Android devices without the sensor, query a weather provider with the user's location.
Units & signal. Relative humidity in % (0–100). Combined with temperature you can derive absolute humidity, dew point, etc.
What You Can Build With It
Plant care apps
Show local humidity to advise on watering schedules.
Example: A houseplant assistant that ties humidity into its care plan.
Asthma and allergy tracking
Correlate symptoms with indoor or outdoor humidity readings.
Example: A respiratory health journal that logs humidity alongside peak-flow values.
Workshop and storage hints
Warn the user when humidity gets high enough to risk wood warping or condensation.
Example: A woodworker's assistant that flags days unsuitable for finishing.
Weather-augmented UIs
Pair humidity with a temperature feed for a richer environmental dashboard.
Example: A travel app that shows comfort indices for upcoming destinations.
Permissions & Setup
No permission required for the on-device sensor. Weather-API fallback needs location.
iOS · Info.plist
No special permission keys required.
Android · AndroidManifest.xml
No special permission keys required.
Code Examples
Setup
- Expo: wrap a small native Android module, or call a weather API for cross-platform humidity
- iOS: no on-device API; use a weather provider
- Android: `Sensor.TYPE_RELATIVE_HUMIDITY` (API 14+) on supported devices
// Cross-platform fallback via weather API
import * as Location from 'expo-location';
export async function getHumidity(apiKey: string): Promise<number> {
const { coords } = await Location.getCurrentPositionAsync({});
const url = `https://api.openweathermap.org/data/2.5/weather?lat=${coords.latitude}&lon=${coords.longitude}&appid=${apiKey}`;
const json = await fetch(url).then(r => r.json());
return json.main.humidity as number; // %
}Tip: With Newly, you describe the feature you want and the AI agent wires up the sensor, permissions, and UI for you. Try it free.
Best Practices
Always feature-detect
Display a different UI on devices without the sensor instead of showing 0%.
Use weather-API humidity by default
For 95%+ of devices, this is the only realistic source. Reserve the sensor for "indoor" overrides.
Combine with temperature for dew point
Dew point is a better signal than raw humidity for "is it muggy?" or "will condensation form?" questions.
Smooth the reading
On-device humidity sensors take 30–60 seconds to settle when conditions change.
Common Pitfalls
No iOS support
A "humidity" app on iPhone necessarily uses a weather API.
Mitigation: Be explicit in the UI that the value comes from a weather provider, not the device.
Phone in a pocket reads body humidity
The user's body adds 5–15% RH to the reading.
Mitigation: Suggest taking the phone out for 1 minute before trusting the reading.
Sensor drift
Humidity sensors drift several % over years.
Mitigation: Document this in your help screen; allow a manual offset.
When To Use It (And When Not To)
Good fit
- Apps targeting users on devices known to include the sensor (rare but real)
- Cross-platform humidity displays via a weather API
- Plant care, allergy, woodworking and brewing apps
- Comfort-index dashboards combining temperature + humidity
Look elsewhere if…
- iOS-only apps that rely on on-device humidity
- Apps that need consistent humidity values across devices
- Sub-percent precision use cases
- Estimating distance from breath, fog, etc.
Frequently Asked Questions
Which phones have a humidity sensor?
Mostly 2013-era Samsung devices (Galaxy S4, Note 3/4) and a small number of ASUS, Samsung Active and rugged industrial Android devices. No iPhone has one.
Why does my reading differ from a hygrometer?
Phone sensors take longer to equilibrate (30–60 seconds), and the user's body warmth in a pocket inflates the reading. Treat it as a rough estimate.
Should I show humidity in my app at all?
Only if it serves the user. If your audience is broad, ship a weather-API-backed display and skip the sensor altogether.
Can I infer humidity from other sensors?
No reliable derivation exists from accelerometer, mic or camera signals. Use a weather API.
Build with the Humidity Sensor on Newly
Ship a humidity sensor-powered feature this week
Newly turns a description like “use the humidity sensor to plant care apps” into a real React Native app — permissions, native modules and UI included. Full source code is yours, and you can publish to the App Store and Google Play directly from the dashboard.
Want a deeper dive on the underlying APIs? See Expo Sensors, Apple Core Motion and Android sensor framework.