Can your iPhone check indoor humidity?

Why iPhones do not have a humidity sensor

Every sensor in an iPhone has to survive being in your pocket, a bathroom, a beach bag, and a hot car. Humidity sensors drift badly after short exposure to liquid water and condensation. Apple chose to leave them out. Samsung, Xiaomi, and most Android phones also leave them out for the same reason.

There are a few rare exceptions. The Samsung Galaxy S4, S5, and Note 3 (2013-2014) had dedicated humidity sensors. They were removed in every later Samsung model. No current flagship from Apple, Samsung, or Google has one.

What the Weather app is really showing

When Apple Weather says "Humidity 68 percent," it is pulling that reading from the nearest National Weather Service observation station. For most US locations, the nearest station is an airport runway. A few things are true as a result:

• Your indoor humidity is almost always different. In summer, air conditioning removes moisture, so indoor typically runs 15 to 25 percent below outdoor. In winter, heating dries the air, so indoor typically runs 15 to 30 percent below outdoor.
• Apartments and basements deviate more. Poor ventilation, bathroom steam, cooking, and laundry all push indoor RH up. A bathroom reading can be 20 points above the outdoor number.
• The outdoor number is still useful. If outdoor humidity is 90 percent and climbing, your indoor will follow a few hours later unless you are running AC or a dehumidifier.

Apps that actually work (they all need an external sensor)

Every iOS app that reports actual indoor humidity is a reader for an external Bluetooth hygrometer. The app itself does not sense anything. The sensor does. You buy the sensor once, it sits in the room, it sends readings to your phone.

The cheapest thing that actually works

If you only care about humidity and do not want an app at all, a basic digital hygrometer costs 10 to 15 dollars at any hardware store. ThermoPro TP49 and AcuRite 00613 are the two usually recommended by home inspectors. They run on a coin battery and show temperature plus humidity on a simple LCD screen. Accurate to plus or minus 2 to 3 percent, which is close enough for mold-prevention decisions.

Place one in each room you care about. Bedroom, bathroom, basement, HVAC return. Check once a week. If any reading goes above 60 percent, take action.

What the number should be

Target indoor relative humidity: 30 to 50 percent. ASHRAE Standard 55 and the EPA both target that range. Mold starts colonizing porous surfaces (drywall, insulation, wood framing, carpet) above 60 percent sustained for 48 hours. Dust mites thrive above 50 percent. Below 30 percent you get dry skin, static, and respiratory irritation.

Once you have the actual number, feed it into our humidity mold risk calculator with your room type. You will get a 0 to 100 risk score, a dew point read, and a personalized fix plan.

If the number is bad, what to do

• 60 to 65 percent: Run bath fans 30 minutes after showers. Run kitchen hood during cooking. Check that dryer vents fully exhaust outside. Open windows briefly during low outdoor RH.
• 65 to 75 percent: Run a 30 to 50 pint dehumidifier sized to the room. Check for plumbing leaks or roof leaks upstream. Consider a sizing calculator.
• Above 75 percent: Serious problem. Use the mold risk index to assess urgency. If any surface is visibly wet or stained, call a licensed mold inspector.

Can you rely on the Siri humidity answer?

No. When you ask Siri "what is the humidity right now," Siri reads Apple Weather, which is the outdoor airport number. It does not measure anything in your home. It is not a hygrometer replacement.

One exception for advanced users: HomePod mini and HomePod (2nd gen)

The HomePod mini (late 2020 and later) and HomePod 2nd gen (2023) have internal temperature and humidity sensors. You can view the reading in the Apple Home app on iPhone. It is real, and it is indoor. But it only shows the humidity in the room where the HomePod lives, and accuracy is plus or minus 5 percent (less precise than a 10 dollar hygrometer). If you already have a HomePod in the room you care about, you have indoor humidity in your Home app. If you do not, buy the hygrometer.