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Live forecasts update automatically; written guidance last reviewed 20 June 2026 by the Headlines UK weather desk. Data from national met services via Open-Meteo.
Live data from Open-Meteo · updates automatically ·
A weather balloon is a high-altitude balloon carrying instruments to measure temperature, humidity, pressure and wind speed in the upper atmosphere. In the UK, the Met Office launches them twice daily from several sites, including a dedicated Balloonport, to feed data into weather prediction models. Check the live forecast above for your local conditions.
How does a weather balloon work?
The balloon is filled with helium or hydrogen and expands as it rises. It carries a lightweight radiosonde – a small box of sensors and a radio transmitter. As the balloon climbs, the radiosonde sends back readings. When the balloon bursts at around 30 km (100,000 ft), a parachute brings the radiosonde back to earth. Many are recovered and reused.
What size and height do weather balloons reach?
A typical weather balloon is about 1.5 metres wide at launch and can expand to over 8 metres before bursting. The weather balloon height reached is usually between 20 km and 35 km. The exact altitude depends on the balloon size and the amount of gas used. For hobbyists, a weather balloon kit often includes a balloon, parachute and tracking module. You can find a weather balloon for sale online, but check the weather balloon price – a basic kit may cost around £100–£300. Some sellers list a weather balloon on Amazon, though specialist suppliers are more reliable for UK delivery.
What is the purpose of a weather balloon?
The weather balloon purpose is to collect upper-air data that surface stations cannot reach. This information is vital for forecasting storms, tracking jet streams and feeding computer models. Without balloons, predictions would be far less accurate. Amateur enthusiasts also use them for near-space photography and science experiments – a popular weather balloon uk hobby that requires careful planning and a CAA permit for flights above 60,000 ft.
How high can a weather balloon go?
Most weather balloons burst between 20 km and 35 km. The record is over 50 km, but standard Met Office balloons reach about 30 km. The exact height depends on the balloon size, gas fill and atmospheric conditions.
Can I buy a weather balloon in the UK?
Yes. Many online retailers sell weather balloon kits, including the balloon, parachute, tracking equipment and sometimes a radiosonde. Prices start around £100. Always check regulations – you may need permission to launch above 60,000 ft in UK airspace.
What data does a weather balloon collect?
A radiosonde records temperature, humidity, atmospheric pressure, wind speed and wind direction at every altitude. This data is transmitted in real time to weather centres and used in forecast models.
Sources
For more UK weather information, see our UK weather hub, 10 day weather forecast or check conditions in Birmingham.