What's that weather balloon doing in the sky? Meteorologist Drew Tuma explains

SAN FRANCISCO (KGO) -- There has been a lot of curiosity about what exactly is flying over us in the sky. Did you know the National Weather Service launches more than 60,000 weather balloons into the atmosphere every year since the 1930s?

More than 90 locations across North America launch weather balloons twice a day, every day, including weekends and holidays.

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Balloons are inflated to 5 feet in diameter with a rope tied at the base leading to a radiosonde at the bottom of the rope.

Radiosondes weigh less than a pound and contain instruments that obtain critical data like temperature, pressure, humidity, wind speed and GPS location every second as these balloons ascend into the atmosphere. That information is relayed to computers back on the ground.

Weather balloons can ascend way up into the atmosphere to altitudes of 115,000 feet. For reference commercial airplanes typically fly around 30,000 feet.

These balloons can also drift more than 180 miles away from their launch point. As they rise in the atmosphere, lower pressure allows the balloon to expand to 20-25 feet in diameter before it pops and the radiosonde drifts back down to the ground.

If you find one of these, they have a prepaid envelope that you can mail back to the weather service.

The invaluable information the balloon collects is input into weather models across the globe -- just like the ones you see on ABC7 which help predict, among other things, where atmospheric rivers will make landfall or which way the winds will blow during times of heightened fire danger.

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