What is hail and how does it get big enough to send people to the hospital?

• Parts of Colorado have been experiencing severe weather, including golfball-sized hail.
• Hail is made of rain and forms when wind causes water droplets to freeze during a thunderstorm.

On Wednesday night, a storm swept across Red Rocks Amphitheater near Denver, Colorado, bringing golf ball-sized hail with it. Up to 90 people were treated for injuries and seven were sent to the hospital from the storm, the Associated Press reported.

The following afternoon, a tornado touched down in Highlands Ranch, Colorado, delivering yet another dose of destructive hail that injured some people, 9News reported.

Colorado is no stranger to severe weather. It has everything from "extreme cold, extreme heat, blizzards, high wind events, seasonal flooding, flash flooding, droughts, forest fires, lightning, hail, and tornadoes," per History Colorado.

But hail is the most common threat in parts of the state during its summer thunderstorm season. It's also costly for insurance companies. One 2017 incident is considered Coloroado's most expensive insured catastrophe, causing $2.3 billion in damage.

What is hail and how can it get so big?

Hail is the Tasmanian Devil of precipitation. It's pure chaos and destruction. But hailstones don't start out that way. They're initially raindrops.

Rain becomes hail when an updraft during a thunderstorm carries the water droplets up into a cold region where they freeze solid.

Depending on the updraft's strength, that tiny chunk of ice can turn into a really big one if it has enough time to grow as more raindrops stick to it.

At some point the hailstone meets a breaking point: it's so large that the updraft can't support its weight and it falls under gravity to Earth.

The largest hailstone in US history fell in 2010 during a thunderstorm in South Dakota. It weighed nearly two pounds and was 8 inches in diameter — almost three times the size of a baseball.

In the US, hail is most common in Nebraska, Wyoming, and — last but not least — Colorado. Where these three states meet is actually called "hail alley," according to NOAA's National Severe Storm Laboratory.

Other regions around the world that experience intense hail include China, Russia, India, and northern Italy.

And like most instances of severe weather, giant hailstones are expected to increase as the globe continues to warm up. Warmer air contains more water vapor for hailstone growth and "powerful storms — with powerful updraughts — also become more likely as weather patterns change," per Euronews.