KinwarnSPC severe weather risk levels: 1 Marginal to 5 High
The Storm Prediction Center rates the severe storm threat on a 1 to 5 scale: 1 Marginal, 2 Slight, 3 Enhanced, 4 Moderate, and 5 High. Higher levels mean more severe storms, stronger storms, or both. Even levels 1 and 2 can include a chance of tornadoes.
Days before a storm, you may hear that an area is under a Slight or Enhanced risk. Those words come from the Storm Prediction Center (SPC), part of the National Weather Service. The SPC forecasts severe thunderstorms and tornadoes for the lower 48 states and shows the threat on a five-level map.
The five risk levels
| Level | Name | Map color | What it means |
|---|---|---|---|
| — | General thunderstorms | Light green | Thunderstorms possible, not expected to be severe |
| 1 | Marginal | Dark green | Severe storms possible but limited: poorly organized and short-lived, or few and not very strong |
| 2 | Slight | Yellow | Organized severe storms, but not widespread; strength varies |
| 3 | Enhanced | Orange | More severe storms than a Slight risk |
| 4 | Moderate | Red | Widespread severe weather, with several tornadoes and/or many severe storms, some intense |
| 5 | High | Magenta | A severe weather outbreak, with many intense, long-track tornadoes or a long-lived derecho |
The SPC describes these levels as progressively larger threats. A higher level can mean more storms, stronger storms, or both.
What the outlook measures
The risk levels come from probabilities. For Day 1 and Day 2, forecasters estimate the chances of tornadoes, damaging winds, and large hail. Those chances are for at least one event happening within 25 miles of a given point, an area about the size of a large metro area.
That is why the numbers can look small. Severe weather is uncommon at any one spot. The SPC says even a 10 percent chance of a tornado within 25 miles is a much bigger threat than usual and should be taken seriously.
Why a Slight risk does not mean safe
The names can be confusing. Slight is level 2 of 5, not the bottom of the scale, and Marginal sits below it.
Tornado chances are part of how even the lower levels are set. According to NOAA, a Marginal risk can be drawn for a 2 percent tornado chance within 25 miles of a point, and a Slight risk for a 5 percent chance. So tornadoes are possible on a level 1 or 2 day.
Two more things to keep in mind:
- Storms do not always stay inside the lines drawn on the map.
- Storms that are not severe can still cause damage.
Day 1, Day 2, and Day 3
- Day 1 covers today through early tomorrow morning. The SPC updates it several times a day.
- Day 2 covers tomorrow.
- Day 3 covers the day after tomorrow.
The SPC also issues a Day 4 to 8 outlook that shows areas with a higher chance of severe storms further out. Outlooks change as the day gets closer, so check again. NOAA notes it is up to each of us to keep checking forecasts.
From outlook to watch to warning
The risk outlook is the first step in a chain:
- Outlook: days ahead, a broad map of where severe storms could happen.
- Watch: hours ahead, issued by the SPC when conditions favor severe storms or tornadoes in a large area. See tornado watch vs. warning and severe thunderstorm watch vs. warning.
- Warning: issued by your local NWS office when severe weather is happening or about to. This is the signal to take action.
How to use the outlook for your family
When a family member’s area falls inside any risk level, use it as a reminder. Check that they know where to shelter, that their supplies are ready, and that they have a way to get warnings. Our family storm plan guide walks through the steps.
See today’s risk map on the severe weather outlook page.