A high risk is the most serious category on the Storm Prediction Center's scale measuring the threat for severe weather on a given day. High risks are reserved for potential tornado outbreaks or derechos, which are long-lived squall lines that produce extensive wind damage along a path stretching for hundreds of miles.

Forecasters at the SPC don't issue high risks lightly. It's tough for the ingredients to come together just right for a major severe weather outbreak to unfold. High risks convey high confidence in a high-impact weather event.

While some of the worst tornadoes in modern history have occurred on high-risk days, it's important to remember that the vast majority of destructive tornadoes and tornado-related injuries and deaths occur on days without a high risk in place. All severe weather is dangerous.

The most recent high risk issued by the Storm Prediction Center appeared during a severe weather outbreak on Monday, May 6, 2024.

The high risk area covered much of Oklahoma and a portion of southern Kansas.

A powerful EF-4 tornado swept through the northeastern Oklahoma towns of Barnsdall and Bartlesville shortly after sunset on May 6. Two people died and several dozen more were injured along the tornado's 40+ mile path.

The initial area under a high risk was west of the EF-4 tornado's path. Dynamics slowly shifted east through the day, and forecasters adjusted the high risk closer toward Tulsa later in the afternoon. The powerful tornado occurred within the high risk area.

This was the 65th day since January 1, 2000, that the SPC has issued a high risk somewhere in the United States.

There have been 224 same-day high risk outlooks issued by the Storm Prediction Center since January 1, 2000, accounting for 65 days over the past two-and-a-half decades. The SPC issues multiple forecast updates throughout the day—this map counts all of those updates.

All of the high risks were issued east of the Rocky Mountains, and the vast majority covered traditional Tornado Alley in the central U.S., as well as portions of Mississippi and Alabama.

The coverage of high risk outlooks since 2000 stands in as a solid climatology for which areas of the country are prone to some of the most extreme severe thunderstorms during the spring and summer months. Only a few areas have seen a single high risk; this includes Virginia Beach (April 16, 2011) and Tampa, Florida (January 22, 2017).

Communities on the central Plains and throughout the Mississippi Valley have witnessed 20-30 high risk areas since the turn of the milennium, with some areas seeing more than 30 individual high risk outlooks.

The maximum number of high-risk overlaps since 2000 appears in northeastern Mississippi, just southwest of Tupelo. These rural communities have fallen under 41 separate high risk outlooks, mostly driven by tornado outbreaks.