What is hail and why does it happen?

Have you ever found yourself wondering, “What is hail and why does it happen?” While we are no weather experts, we do know a thing or two about these hailstones and how they interact with your home. 

If you’re a homeowner, you probably cringe at the thought of any calamity that could cause an insurance claim or displace you from your home. Hailstones can damage or destroy gutters, cars, patio furniture, house siding, crops, and roofs. The damage caused by hail depends on a number of factors including the size of the hailstones, speed and direction that it is falling, as well as the density/weight of the hailstone that falls to earth. The largest hailstone in the United States fell in Vivian, South Dakota in June of 2010 weighing in at 1 pound and 15 ounces with a diameter of 8 inches and a circumference of 18.62 inches! Imagine what that would do to the roof of your house, you’d likely have a gaping hole in your roof!

What is hail and what causes it?

Hail forms when supercooled water droplets are carried upward into thunderstorm clouds by updrafts. These once raindrops are then forced into the extremely cold areas of the thunderstorm and freeze. This cycle repeats itself causing the hailstones to then grow by colliding with liquid water drops that freeze onto the hailstone’s surface. Hail commonly happens in mid-latitudes throughout the summer when surface temperatures are warm enough to promote the instability associated with strong thunderstorms and the upper atmosphere is cool enough to support the formation of ice. 

The hail falls to the ground when the thunderstorm’s updraft can no longer support the weight of the hailstone. Smaller hailstones can be blown away from the pathway of the updraft by horizontal winds. If the updraft weakens it will also cause the hail to fall to the ground. Many people falsely believe that only the top of things could get damaged by hail, but this is incorrect. Wind-driven hail can break windows, ding up the sides of your car, and tear up siding on houses if it falls at an angle.

How big does hail get and how do you size it?

Depending on how many times the hailstones are recirculated through the thunderstorm and if it attaches itself to other hailstones will determine the size of hail that falls on your property. The typical sizing of hail is done by comparing it to common circular shaped items. Of course, hail is rarely a perfect sphere especially when two or more hailstones stick together to form a bigger hailstone. Below are some of the typical size comparisons used.

  • Pea = 1/4 inch diameter
  • Penny = 3/4 inch diameter
  • Nickel = 7/8 inch
  • Quarter = 1 inch — hail quarter size or larger is considered severe
  • Ping-Pong Ball = 1 1/2 inch
  • Golf Ball = 1 3/4 inches
  • Tennis Ball = 2 1/2 inches
  • Baseball = 2 3/4 inches
  • Softball = 4 inches
  • Grapefruit = 4 1/2 inches

How fast does hail fall?

It is very difficult to say exactly how fast hail falls because of all the factors you have to take into consideration. Some of those factors include: the size of the hailstone, the air pressure around the thundercloud, local wind conditions, and any melting the hailstone may be doing on its decent. As one would expect, due to gravity, the larger and heavier hailstones often fall faster than the small pea-sized hailstones. Decent speeds ranges from 9 to 25 miles per hour (mph) for the small hailstones that are less than 1inch in diameter to over 100 mph for hailstones that exceed 4 inches in diameter.

What areas have the most hail?

Hail can happen anywhere, though in the United States of America it occurs the most in Nebraska, Colorado, and Wyoming. “Hail alley” – is the common name for the area where these three states meet and averages seven to nine hail days per year. We recommend paying attention to your local weather for when to expect hail to hit your area or other weather events that can cause damage to your home or property. Other parts of the world that have damaging hailstorms include China, Russia, India and northern Italy.

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