A weather balloon kit consists of a weather balloon and a device used to measure various aspects of the weather. The balloon is usually latex or synthetic rubber (neoprene) and filled with hydrogen or helium. A radiosonde attached to the balloon measures factors such as temperature, pressure and relative humidity.
Weather balloons are released daily from over 900 locations around the world. The National Weather Service releases 92 of these balloons in the United States and its territories. Flights last approximately two hours, can travel up to 125 miles away, and rise up to 20 miles high in the atmosphere.