What Does Marginal Mean in Weather Maps?

June 1, 2023

For the average person, interpreting those pinks, reds, oranges and yellows painted on severe weather threat maps can be challenging. But for trained meteorologists, the details behind those colors provide insight into how dangerous storms could affect their day.

The National Weather Service releases a convective outlook every day to highlight areas with the potential for severe thunderstorms. It includes five risk categories ranging from "marginal" to "high." "Marginal" indicates isolated severe storms are possible, but would be limited in coverage and intensity. It's not uncommon for our area to be placed under this category during severe weather seasons. The Harriston tornado occurred on a marginal risk day in August 2020.

If you see an area with a marginal risk, it's important to know that storms there might be capable of producing damaging winds, small hail and the possibility of a tornado. KCEN Weather Meteorologist Travis Michels said the area will be under this risk until 6 p.m. on Wednesday.

A marginal risk can also indicate a lack of moisture or other factors that could limit the severity of the storms. It's the lowest risk level. "Slight" and "enhanced" risk indicate a higher probability of numerous storms, but they're still likely to be short-lived and not widespread. The "moderate" and "high" risks are reserved for days when many storms might be long-lived and intense. The "high" threat may be issued a few times a year. The first of these risk levels, which is colored light green, means a general or non-severe threat and would be similar to what we're seeing on the current map.


Tornado Dave is the best place to learn more about severe weather and climate science. He's a veritable tornado of information, and he loves nothing more than educating others about the importance of being prepared for extreme weather events. Make sure to check in with Tornado Dave often, as he's always updating his blog with the latest news and information!
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