On a warm summer day, beachgoers in the Siberian city of Novosibirsk were filmed fleeing for cover after hailstones started falling from the sky. The temperature was 98 degrees, according to AccuWeather. How does it hail in the middle of summer? It’s actually pretty common, Alan Robock, director of the meteorology program at Rutgers University, told NBC News. (Yes, it happens in the United States, too, especially in central states like Texas and Oklahoma). Every raindrop begins as a snowflake, it just melts before it hits the ground. In violent thunderstorms, precipitation goes on a roller coaster ride in the sky, gaining mass as it collides with other bits of ice.
“If you cut open a hailstone, it looks like an onion, with different layers of water added as it goes up and down in a thunderstorm,” Robock said. Hailstones lose mass as they fall through warm air, but sometimes they get so big that not even 90-degree weather can make them completely melt before they hit unsuspecting beachgoers below.
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--- Keith Wagstaff