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Updraft® - Minnesota Weather News
Mandy Thalhuber

Severe Weather Awareness Week: Severe storms, lightning and hail

Severe weather hazards
Severe weather hazards
National Weather Service

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April 7-11 is Severe Weather Awareness Week. It’s a time where we help educate the public about severe weather preparedness, safety and the importance of weather awareness. Let’s take a closer look at severe storms, lightning and hail.

Thunderstorms

Each year, about 100,000 thunderstorms occur, with roughly 10 percent of those becoming severe. The National Weather Service classifies a thunderstorm as severe if it produces hail at least 1 inch in diameter, winds of 58 mph or stronger, or a tornado.

The typical thunderstorm is 15 miles in diameter and lasts around 30 minutes, and it can be deadly and cause significant damage. Thunderstorms commonly occur in the spring and summer months during the late afternoon and early evening hours, but they can happen year-round and at any time, day or night.

Lightning

Every thunderstorm produces lightning. While most lightning occurs within the clouds, lightning that strikes the ground is the most dangerous. Ground strikes can cause fires, power outages and serious injuries or fatalities, making them the most concerning during a storm.

Lightning is hotter than the surface of the sun. This intense heat causes the air around the strike to rapidly expand, creating a sound shockwave known as thunder. It’s important to remember, “when thunder roars, go indoors.”

A lightning bolt
A lightning bolt strikes in Iowa.
Kevin Skow | Courtesy of NOAA

Damaging winds

Thunderstorms can also produce damaging winds, including straight-line winds and derechos. Straight-line winds are powerful, nonrotating winds that move in a straight path. Wind speeds from straight-line winds can reach up to 100 mph.

A derecho is a widespread, long-lived windstorm associated with a band of rapidly moving showers or thunderstorms.

Both derechos and straight-line winds can produce significant damage.

Derecho radar sequence
August 10, 2020 derecho radar sequence
Chicago NWS

Hail

Hail is another common feature of severe thunderstorms. Hailstones can range in size from pea-sized to grapefruit-sized or even larger. The largest hailstones can fall at speeds approaching 100 mph, which can cause significant damage.

One of the largest hailstones in Minnesota was recorded just this past July in Chokio. The hailstone measured nearly 6 inches in diameter.

Hail, damaging winds and lightning are all common and dangerous features of severe thunderstorms. It is important to know what safety measures to take to ensure your safety. Always be prepared!