Calculator

Humidity today

Choose a location to see the current outdoor reading.

Readings come from Open-Meteo, an open weather API — not from Apple Weather, which is what the iPhone app uses. The two model and interpolate differently, so expect small differences between this page and the app. Your coordinates are sent to Open-Meteo to fetch the reading and are not stored here.

The figures above are the answer for the values this page loaded with. Changing the controls needs JavaScript — without it the calculator cannot recalculate, so read them as one worked example rather than a live result.

What is the humidity right now?

Choose your location above and the reading appears: the current outdoor relative humidity, the dew point behind it, the grams of water per cubic metre the air is carrying, and how much margin is left before that water starts condensing. Readings are outdoor conditions from Open-Meteo.

What you are looking at

The large figure is relative humidity: how close the outdoor air is to holding all the water it can at its current temperature. It is the number every forecast quotes, and on its own it is famously hard to interpret — which is why three more sit underneath it.

Dew point — the temperature this air would have to reach before saturating. Unlike the percentage, it is a direct measure of how much water is present, and it stays nearly flat all day. If you check one number, check this one.
Water in the air — grams per cubic metre, the actual quantity. This is what makes today comparable with a day in January.
Margin to saturation — the gap between the air temperature and the dew point. When it closes to about a degree you get mist and fog; while it is wide, only genuinely cold surfaces collect water.

Why the percentage on its own misleads

A reading of 80% sounds high, and in February it usually means the air is nearly empty — cold air saturates at a very low water content. A reading of 50% in July can mean considerably more water in the air than that 80% did.

This is not a subtlety; it is a factor of several. It is why the app shows the grams alongside the percentage, and why dew point beats humidity for almost every practical question about how a day will behave.

Where these numbers come from

This page reads Open-Meteo, an open weather API, directly from your browser. It is not the same source the Hygrometer app uses — the app reads Apple Weather — and the two will differ slightly for the same place and time, because they interpolate between observation stations differently.

The derived figures are computed here, in your browser, using the same implementation the app runs. So the dew point on this page and the dew point in the app agree about the arithmetic even when they start from slightly different observations. The longer version of that answer is where the humidity data comes from.

What this cannot tell you

It cannot tell you the humidity in your house, and it does not try. Indoor humidity is a product of the building — the heating, the ventilation, how many people are in it, whether anything is drying — and measuring it requires an instrument in the room. What an outdoor reading does tell you is what the air arriving through an open window is carrying, which is often the more actionable half.

Common questions

What is the humidity right now where I am?

Use the location button above, or search for your town. The figure that appears is the current outdoor relative humidity at your coordinates, with the dew point and the absolute humidity underneath so the percentage has some context.

Is this the humidity indoors or outdoors?

Outdoors, always. Nothing in a browser or a phone can measure the room you are standing in — neither has a humidity sensor — so this reads an outdoor weather service for your location. Indoor humidity depends on your heating, ventilation and what is happening in the building, and needs a physical instrument in the room.

Why is this reading different from my weather app?

Different providers use different stations, different models and different interpolation between them. This page reads Open-Meteo; Apple Weather, which the Hygrometer app uses, will give a slightly different figure for the same place and moment. Humidity also varies sharply over short distances, so two nearby readings can genuinely disagree.

Do you store my location?

No. Your coordinates are sent to Open-Meteo to fetch the reading and are used for nothing else. There is no account, no cookie and no analytics on this site.

Why does the humidity change so much during the day?

Mostly because the temperature does, not because water is arriving or leaving. Relative humidity measures how close the air is to saturation, and the saturation point roughly halves for every 10°C of cooling — so the same air reads much higher at dawn than at three in the afternoon. The dew point beside it barely moves, which is why it is the better figure to watch.

Sources

Open-Meteo — open weather API — Source of the readings on this page

Published 31 July 2026