In less than 20 minutes, a Colorado car dealership’s entire inventory was destroyed by golf ball-size hail. On May 8, 2017, emergency alert sirens shrieked from cell phones across Denver. Minutes later, employees stood transfixed as the “Hailstorm of the Century” slammed into a luxury car dealership. Golf ball-size hail smashed windshields and windows. It pounded deep dents in the roofs and hoods of every single car on the lot, and hammered the metal roof on the showroom.

By the end of the storm, nearly 400 cars (many priced in the six-figure range) were completely totaled. The loss — 100 percent of the dealer’s inventory — and damage to four buildings rang up $3 million in damages. The dealership’s business was at a complete standstill for nine days.

Hail Isn’t Just about Property Damage

Seeing the destruction hail can wreak on steel, it should come as no surprise that it’s a dangerous force against humans too.

If a person is struck by a 2-inch hail ball, severe bruising is a certainty, and broken bones are a possibility says Dr. Ian Giammanco, lead research meteorologist at the Institute for Business and Home Safety (IBHS). “Larger hail can cause even more severe injuries. Hailstones over 3 inches can kill people and livestock.”

Do You Live in a Hailstorm Zone?

Hailstorms are most common in Tornado Alley — the Midwest and Great Plains areas east of the Rocky Mountains. But they can happen in any part of the country when conditions are right.

Landlocked states in the Great Plains and the Midwest are most frequently impacted by hailstorms. That’s because hail commonly occurs in regions where the air’s freezing altitude dips below 11,000 feet.

The region where Nebraska, Colorado and Wyoming meet tops the list as the most common location for hailstorms. It is appropriately known as Hail Alley. The city of Cheyenne, Wyoming, experiences more hailstorms than any other city, with upwards of 10 hailstorms a year.

Hailstorms can occur during the spring, summer or fall months. The majority of these storms appear between May and September.

Hailstorms Across the U.S.

Rich Cavaness, a project manager at a company that specializes in roof construction and repair in Plano, Texas, saw what 60-mph, wind-driven hail the size of a softball can do to a home after the 2016 Wylie, Texas, hailstorm. Hail punctured holes in siding and shattered windows. It cut through shingles, roof decking, insulation and ceiling material, then bounced around inside homes, damaging furniture and flooring in its final impact. “The hail was so large, entire homes were written off as a total loss.”

How Big (and Fast) is Hail?

The size of a hailstone affects its falling speed, referred to as terminal velocity.

  • 1-inch hailstone (quarter) potential terminal velocity = up to 50 mph
  • 5-inch hailstone (tennis ball) potential terminal velocity = up to 80 mph
  • 3-inch hailstone (orange) potential terminal velocity = up to 90 mph

Are you Prepared for the Next Hailstorm?

Preparation and safety procedures can help minimize damage.

  1. Know the rating of your roofing shingle. Imagine firing a 2-inch steel or ice ball at a roofing shingle at 70 mph. Roof coverings with a Class 3 or Class 4 rating withstand this rigorous testing in order to receive those high ratings. When researching high-quality roofing material, if you live in a hail-prone region, IBHS recommends considering a Class 3 or Class 4 rated roof covering, such as slate or tile with a FM 4473 Class 4 hail rating; or, metal or asphalt shingles with UL 2218 Class 4 impact rating.
  2. Protect expensive equipment outside your home or business. Think about equipment sitting outside or on the roof, such as commercial or residential HVAC units, exhaust fans and vents. Hail guards or hail netting can protect these investments and pay for themselves by preventing total losses.
  3. Find the safest places in a hailstorm. Hail warnings are typically triggered up to 30 minutes prior to a storm, but weather apps rely on a single computer model forecast and can share inaccurate information. Local television and radio broadcast weather information can supplement these apps with the most up-to-date information about a storm’s approach and capabilities.

How to Know If a Hailstorm is Coming

In order for a hailstorm to occur, atmospheric conditions must be right. Thunderstorm clouds must be present. In order to produce hail, they must have high moisture content and a large portion of their cloud layer must be at freezing temperatures. Meteorological readings can often predict when a hailstorm is on the way.

If you are concerned about an upcoming hailstorm, your first step is to listen to a weather report. If you are away from a television or a radio, then look to the sky. Gray clouds, rain, thunder or lighting are all signs of a possible hailstorm. You should also take note if you feel a sudden drop in temperature. Cold fronts are a strong indicator that hail or other forms of severe weather are on their way and that you’ll be safer indoors.

When a Hailstorm Alert is Issued

Stay away from windows. Avoid going outdoors in a hailstorm.

If you can’t seek shelter indoors. Get under trees and branches, which may break up the hail and slow its descent. Find a gas station, car wash, carport, retail store or restaurant. If you can’t find shelter, cover your head with your arms to help protect your head as best you can or find a covered parking spot.

Avoid stopping under an overpass if you’re driving — a common instinct for drivers. The threat of a serious traffic accident under an overpass is far greater than hail damage to your car.

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