What is Hail?
Hail is a type of precipitation that gets caught in strong winds that are moving up. When it starts to fall, more water droplets attach to the balls of ice. Then, more strong winds push the chunks of ice up again and the tiny ice crystals form another layer. Hail can be perfectly round or uneven in shape.
How Does Hail Form?
The formation of hailstones happens when drops of water freeze in the top part of the cloud. Strong updrafts take the ice balls up to cold areas of the upper atmosphere and more water vapor turns into ice pellets. Big hailstones form as they get caught in wind gusts over and over again adding another layer of ice each time. The stronger the updrafts are then the bigger the hail will be.
Sometimes in freezing air, water droplets will combine with the hailstone and freeze instantly. When this happens, the hail is cloudy because it has air bubbles in it. If the freezing happens slowly, then the hailstones will actually be clear. The next time you see hail pay attention to if it is clear ice or cloudy ice and then you will know why.
Hail in Warm Weather
Hail happens in the Fall, Spring, and Summer seasons. You wouldn’t think ice would fall from the sky in warm weather, but it does. Even if the air temperature is warm, if the upper atmosphere is still cold then hail can form. If thunderstorm updrafts push the water vapor up into the cumulonimbus clouds (storm clouds) then it will freeze and create a hail storm. Hail is actually most common in the months of May, June, July, and August.
If you were looking down from the sky, you would be able to see the path of a hailstorm. The path of a hailstorm is called hail swaths. There are even HailSWATH maps that you can look at for information about where different sized hail has fallen and the most common days of hail.
Where Does it Hail the Most?
Smaller hailstones can happen during thunderstorms with gusty winds and heavy rain anywhere. However, large hailstones aren’t as common. Although hail can happen anywhere, there are certain parts of the world that have a better chance of seeing hail every year.
Colorado, Nebraska, and Wyoming are three states that people have nicknamed Hail Alley. These states can see hail several times (6-10) each year. That’s a lot!
In fact, Cheyenne, Wyoming is known as the hail capital of the United States because it hails there so often. Other countries like Northern Italy, China, Russia, and India also see hailstorms. The city of Kericho in Kenya holds the record for the most days with hail (132 days in one year).
Depending on the size of the hail or wind speeds during a hailstorm, a lot of damage can happen. This is called hail damage. During heavy hailstorms, extreme damage can occur. Power lines can go down causing the power to turn off at your house. Larger hails can fall and reach speeds of up to 100 miles per hour. Hail could break windows or dent cars and roofs.
Size of Hail
The size of hail can be small like the size of a jelly bean, medium sized like a golf ball, or even large like the size of baseballs. Hailstones measuring .2 inches to 6 inches are the average size. The largest hailstone ever recorded was 8 inches. The heaviest weight of a hailstone to be recorded is about 2 pounds.
Warning Signs of Hail
Predicting hail is very difficult for scientists. Days that have warmer temperatures (warm air) and mid to high humidity (moist air) can create hail.
In the United States, the National Weather Service keeps an eye on the weather and can issue a severe thunderstorm warning which will help people prepare for severe thunderstorms and the possibility of hail. They call it severe hail if it is larger than 1 inch.
Fun Facts about Hail
- The bigger the hailstone is, the higher in the sky it fell from.
- Hail usually starts very suddenly and only lasts a couple of minutes.
- If you cut a hailstone in half you will see different rings. The number of rings will tell you how many times it traveled to the top of the storm cloud. This is similar to how tree trunk have rings to show how many years they have lived.