Why is there a secondary peak of severe weather in the fall?

By Brian Lada, AccuWeather meteorologist and staff writer

October 08, 2017, 10:03:31 AM EDT

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While spring is the most active time for severe thunderstorms across the United States, autumn brings another heightened risk of severe weather, particularly across the Southeast.

“The second severe peak happens in the fall because you see the jet stream starts to shift southward in response to the Northern Hemisphere cooling off,” AccuWeather Southeast Weather Expert Frank Strait said.

Severe thunderstorms during the fall can be just as violent as those in the spring, bringing the threat of tornadoes, damaging winds and flooding downpours.

“It's typical to see one or two significant severe storm events in fall,” Strait said.

The southern United States is the area of greatest concern for severe weather in the fall as cold fronts diving from the north collide with warm, humid air originating from the Gulf of Mexico.

While the most common area for severe weather in the fall ranges from Texas to Georgia, some storms occasionally impact areas farther north, including the central Plains and the Mississippi Valley.

“Even the mid-Atlantic region and lower Hudson Valley can get [severe storms] at times in October and November,” AccuWeather Lead Long-Range Forecaster Paul Pastelok said.

In some cases, early winter storms diving into California can breed severe weather along part of the West Coast.

Tropical systems also contribute to the secondary peak of severe weather along the Gulf Coast, including the risk of tornadoes, according to Pastelok.

However, the risk of severe weather from tropical systems slowly diminishes throughout the fall as the Atlantic hurricane season comes to an end on Nov. 30.

A truck lies on its side in a neighborhood in Washington, Ill., Monday , Nov. 18, 2013, after a tornado hit the area on Sunday damaging or destroying as many as 500 homes. One death was confirmed in the town as a result of the storm. Illinois was the hardest hit by the unusually powerful late-season wave of thunderstorms that brought damaging winds and tornadoes to 12 states. (AP Photo/Armando Sanchez)

Even though severe storms primarily impact the southern United States in the fall, those farther north should not let their guard down.

On Nov. 17, 2013, a severe weather outbreak led to 73 tornadoes from Tennessee to Illinois and Michigan, including seven EF3 tornadoes and two EF4 tornadoes, according to Strait.

This was one of the largest severe weather outbreaks for the state of Illinois, causing widespread damage and multiple fatalities.

Multiple tornadoes touched down in northwestern Oregon on Oct. 14, 2016, an uncommon severe weather event for the area that damaged over 100 homes.

“[People] should keep in mind that severe weather can occur on any day of the year,” Strait said.

For more safety and preparedness tips, visit AccuWeather.com/Ready.

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