How often has this happened to you? You’re trying to plan some outdoor recreation — perhaps a picnic, or a hike, or a day at the beach — and the forecast calls for “isolated thunderstorms.” You scratch your head, wondering whether or not to cancel your plans.
Weather reports can be tricky to understand if you don’t know the terminology. We’ll break it down for you, so that the next time you see one of these terms, you’ll be weather wise and know what they mean!
Isolated thunderstorms: The National Weather Service uses the term “isolated” to describe a less than 30% chance of measurable precipitation (0.01 inch) for a given location.
Likely thunderstorms: The National Weather Service uses the term “likely” to describe 60% or greater probability of measurable precipitation (0.01 inch) for a given location.
Scattered thunderstorms: The National Weather Service uses the term “scattered” to describe a 30% to 50% chance of measurable precipitation (0.01 inch) for a given location.
Severe thunderstorm: To be classified as severe by National Weather Service standards, a thunderstorm must meet ONE of the following three criteria: wind speeds reach 58 mph or faster; hail is three quarters of an inch in diameter or larger; or if the thunderstorm produces a tornado or tornadoes. Even if a thunderstorm is not classified as severe, lightning and heavy rain can still pose a danger.
Severe thunderstorm warning: Severe thunderstorms are occurring or will definitely occur in the warning area. A severe thunderstorm has been detected Doppler weather radar or seen by official Skywarn spotters or other designated persons, such as local law enforcement.
Severe thunderstorm watch: Severe thunderstorms are possible in and around the watch area. A watch does not mean that thunderstorms will definitely occur, just that conditions are favorable for the development of severe thunderstorms.
Jaime McLeod is a longtime journalist who has written for a wide variety of newspapers, magazines, and websites, including MTV.com. She enjoys the outdoors, growing and eating organic food, and is interested in all aspects of natural wellness.