Severe Thunderstorms

All thunderstorms produce thunder and lightning. Of all types of severe weather, lightning is the number one killer, so all thunderstorms should be treated with caution.

Thunderstorms are also capable of producing hail, strong winds and heavy rain. When a thunderstorm's winds or hail become strong enough to cause damage or injuries, the storm is officially “severe”. This happens at wind speeds of 58 miles per hour or hail one inch (quarter sized) and larger.  A severe thunderstorm warning may be given to let people know of the dangerous conditions.

In addition to lightning, hail and winds thunderstorms can also cause power outages, tornadoes and flooding.

Learn more about severe thunderstorm dangers (PDF) and check out Ramsey County's Get Ready page for information on thunderstorm watches and warnings, severe weather warning sources such as outdoor warning sirens, and severe weather emergency plans for your home or business.

Facts about thunderstorms

• Thunderstorms in our area of the country are normally anywhere from 20,000 to 50,000 feet tall. The taller they are, the more energy they likely have to produce severe weather. Most single thunderstorms (called cells) are about five to 20 miles across. 
• During the warmer months we get most of our thunderstorms in the mid- to late afternoon, from 4-7 p.m. But they can occur any time of the day. They also can occur in any month as long as there is enough warm moisture to form clouds big enough to have lightning, but our peak thunderstorm season is May to June. Lightning can even happen in a snowstorm: it’s called thundersnow.
• Thunderstorms can form very quickly, in as little as 30 minutes. This is why it’s important to keep an eye on the weather if there's a chance of storms – things change very quickly. Most storms last only about 30 minutes, but multiple storms in the same area can make it seem a lot longer. 
• Thunderstorms are huge. They can hold 275 million gallons of water in them, weighing 2.3 billion pounds. 
• Most storms travel approximately west to east. They can travel as quickly as 60 miles per hour (ground speed). 
• Lighting is only about the width of a pencil. A single bolt has billions of watts of energy in it and can heat the air around it to 60,000 degrees Fahrenheit. The shock wave of this rapid heating is heard as thunder. In the U.S. there are 20,000,000 lighting strikes that hit the ground every year. This makes lighting exceptionally dangerous.