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Conditions

About this measurement

Groundcheck in FirefoxSee the nearest weather balloon reading from your toolbar, and search Flowsearch from the address bar. Free.

Credits

Weather data

sonde.mine.nu / zeesen.mine.nu

Live radiosonde telemetry from a public tracking network run by volunteers with their own receivers. sonde.mine.nu

SondeHub

An open, worldwide database of radiosonde telemetry, fed by hundreds of volunteer receivers. It gives Groundcheck readings from North and South America, Asia, Australia and more. sondehub.org

NOAA IGRA

The Integrated Global Radiosonde Archive of NOAA's National Centers for Environmental Information: the official soundings of about 650 weather-service stations in more than 100 countries (public domain). NOAA NCEI

Maps & places

Esri

Map imagery © Esri, Maxar, Earthstar Geographics and the GIS user community. esri.com

OpenStreetMap

Place search and place names come from Nominatim, using © OpenStreetMap contributors data. openstreetmap.org/copyright

Leaflet

The map is drawn with Leaflet (BSD-2-Clause) and Leaflet.markercluster (MIT). leafletjs.com

DB-IP

If you do not share your exact location, an approximate one is looked up from your IP address on our own server with the free IP to City Lite database. Your IP is not stored. IP Geolocation by DB-IP

Design & code

Fonts

Sora and Inter, from Google Fonts, under the SIL Open Font License.

Open source

Groundcheck is free software under the AGPL-3.0 licence. The source code is on GitHub.

Projects we make

Flowsearch

A search engine we made ourselves: its own crawler, its own index and its own ranking, with a German and an English version. Open Flowsearch · Source on GitHub

Good to know

Forecasts can be wrong

Measurements come straight from weather balloon sensors. The Next days forecast is an estimate that Groundcheck calculates from collected readings, with no weather model, and it can be wrong. Its typical error is shown next to it.

Thank you

To everyone who builds, launches, hosts and runs radiosondes and receivers. Without them there would be nothing to show.

FAQ

Why use this?

You get to see real, live sensor data straight from actual weather balloons in flight right now — the same raw measurements meteorologists use to calibrate forecasts. It's a genuine look at the atmosphere, not a prediction.

Where does this data come from?

Live radiosonde (weather balloon) telemetry from sonde.mine.nu (its sondes.php feed) from SondeHub (sondehub.org, an open worldwide database of radiosonde telemetry) and from NOAA's Integrated Global Radiosonde Archive (IGRA), the official soundings of about 650 weather-service stations in more than 100 countries — real sensor readings from balloons currently or recently in flight, not a forecast model.

Why are some temperatures missing from the list?

Radiosondes spend most of a flight at high altitude, where it's routinely −40°C to −70°C. Those readings aren't representative of ground weather, so this app filters them out and only keeps readings at or above 0°C and at or below 980 m — taken just after launch, on the way down, or after landing.

Why does it say a station is far from me?

This isn't a dense ground-sensor network — it's wherever balloons happened to fly recently. If nothing launched near you in the last 7 days, the nearest valid reading may be hundreds of km away. The app always labels the distance honestly instead of pretending it's local.

Why does location sometimes look approximate?

Precise GPS location requires a secure (HTTPS) connection. If you're on a plain http:// address, the app falls back to IP-based location, which is only accurate to city level.

How often does data update?

The server fetches the live feed every minute, SondeHub about every five hours and NOAA IGRA once a day. The page itself checks for new data every 5 minutes.

What do Humidity/Pressure show "—"?

Not every sonde model carries a working humidity or pressure sensor — some report temperature only. A dash means that particular sensor had no data, not an app error.

Groundcheck: live weather measured by weather balloons

Groundcheck is a weather app whose numbers are measurements, not model output. It shows the temperature, air pressure and humidity that weather balloons (radiosondes) recorded close to the ground, around the world, as a map, a list and a weather screen for your location.

Use it every day

Open it to see the real temperature near you right now. The Today screen shows the nearest recent balloon reading, how far away it was taken and how old it is, so you always know how much to trust it. The server fetches the live feed every minute, and the app checks for new data every five minutes. New readings arrive all day, several hundred per day worldwide, because balloons come down and land continuously. They are not tied to the two big launch times of 00:00 and 12:00 UTC.

What counts as a ground-level reading

Only readings taken at or below 980 m above sea level, and at or above 0 °C, are kept. They come from balloons that are close to the ground: just after launch, on the way down, or after landing. The freezing readings from high in the atmosphere (often −40 °C and colder) are left out because they say nothing about the weather where you are.

Where the data comes from

The live radiosonde feed of sonde.mine.nu (fetched every minute), amateur balloon tracking from SondeHub (about every five hours), and the NOAA IGRA archive of official weather-service launches (daily). Together they cover several hundred stations across Europe, North and South America, Asia, Australia and more.

The forecast

Groundcheck's own forecast for the next hours and days, called "Next days", is built only from these balloon readings (seasonal normals, how today differs from normal, and the pressure trend). It does not use a weather model and it can be wrong. The accuracy page shows how the big weather models scored against what balloons measured.

How it differs from a normal weather app

A normal weather app gives radar, hourly rain chances and warnings from computer models. Groundcheck gives measured values and an honest distance to the nearest reading, and it has no radar or alerts. Many people use it next to a regular weather app, to check what was really measured.

Free to use

The web app, the Firefox add-on, a public data API, and a self-host package to run your own copy. We also make Flowsearch, a search engine with its own crawler and index. See also the 3D globe of every reading.