Weather balloons are released from around a hundred sites in the US twice a day. Additionally, about 1,300 other stations launch twice a day for weather forecasts and other scientific or military purposes. All stations launch at least twice a day at 00Z and 12Z (7 a.m. and 7 p.m. CST), with other launches happening as needed.
The radiosonde is an electronic device used to measure wind speed, air temperature, humidity, and pressure. These hang below a balloon filled with hydrogen or helium and ascent up into the stratosphere. Eventually, the balloon bursts, and the radiosonde falls back to earth under a parachute.
An average weather balloon flight can last over two hours, some going a bit longer or shorter depending on conditions. These flights can reach altitudes of over 115,000 feet (35,000 m) and drift more than 125 miles (200 km) from their release point, and are exposed to temperatures as cold as -130°F (-92°C) and extremely low air pressures.
Most radiosondes in the US transmit their weather reading and GPS data via radio within the 400-407 MHz range. There are several projects available to enable the tracking of these balloons.
https://sondehub.org/ Is the site that I use to track weather balloons. This site allows you to see the current path with a projection of where it will land. Additionally, you can make that you recover one if you do so.
Here is the presentation I gave at the AA5RO meeting.
The map below shows the sondes I have tracked and attempted recovery of. Red is not recovered after an attempt, Yellow I haven’t attempted yet, and Green is successfully recovered.