A weather balloon is a large, inflatable balloon filled with helium or hydrogen that is used to collect data about the atmosphere. As it rises, it carries instruments called radiosondes that measure temperature, humidity, and atmospheric pressure. This information is crucial for weather forecasting and understanding climate patterns. Typically launched from weather stations, weather balloons can reach altitudes of up to 30 kilometers (about 18 miles) before they burst. Once they pop, the instruments fall back to Earth with the help of a parachute. The data gathered helps meteorologists improve predictions and monitor changes in the atmosphere.