Recent years show that tornadoes are a risk in the fall and winter

Tornadoes and severe thunderstorms are most common in the United States in the spring and summer, but they can also occur in the fall and winter, whenever conditions are right.

This statement may be surprising. Autumn usually conjures visions of the season’s first cold fronts sweeping away summer heat and humidity. Cool, quiet fall mornings don’t seem to go with thoughts of severe thunderstorms.

And let’s face it, the cold and snow of winter seems to be the exact opposite of tornadoes.

The data tells a different story: Below is a graph of average monthly tornadoes in the United States over the last 20 years through 2022.

Yes, there is a clear peak in spring and early summer. But, although lower than in the spring, tornado numbers remain fairly constant in the fall and winter. The average number of tornadoes per month in those seasons is more than thirty tornadoes each year.

Just like spring, fall is a season of battle: Tornado numbers do not drop to zero after the summer because the conditions that generate them still occur in the fall and winter in some parts of the country.

Larger outbreaks occur when warm, moist air from the Gulf of Mexico meets increasingly powerful cold fronts and jet stream winds that typically sweep across the country. This is generally the same setup we often see in the spring.

When this combination of ingredients comes together, it can ignite numerous severe thunderstorms that produce damaging winds, large hail, and tornadoes.

October tornado risk could still extend to the north: Although this does not happen every year, tornadoes are more likely to reach the upper Midwest and Northeast during the first full month of fall.

Among the recent outbreaks in October were an outbreak from October 20 to 21, 2019, in six southern states, including an EF3 on the north side of Dallas; The largest outbreak in Pennsylvania in October 2018 and an outbreak in early October 2013 that spawned an EF4 tornado in Wayne, Nebraska.

Greatest tornado risk in November shifts south: Parts of the South, especially the lower Mississippi Valley, face the greatest risks. But the potential for tornadoes could extend north into the Mid-Mississippi Valley, Lower Ohio Valley and Mid-Atlantic states.

November 2022 was a reminder with an above-average 68 tornadoes per month, most of which were in the South. The deadly tornadoes struck Texas and Oklahoma on November 4, then Alabama early on November 30.

One of the nation’s worst tornado outbreaks occurred just days before Thanksgiving in 1992 when a swarm of 105 tornadoes tore through parts of 13 states from Texas to the Carolinas. The severe weather killed 26 people and injured 638 others.

Winter hurricanes are also a concern, especially in the South: As expected, Arctic cold fronts often stream through the South in the winter, preventing any chance of thunderstorms — let alone severe thunderstorms — in the Lower 48.

But when that cold air doesn’t penetrate parts of the South in winter, an active jet stream interfering with warmer, more humid air can ignite severe thunderstorms before a cold front advances.

December 2021 was the latest extreme example, and not just for the South. Two extreme weather waves hit parts of the South and Midwest in just five days in mid-December 2021.

The first outbreak of 66 long-track tornadoes included Mayfield, Kentucky, and an EF4 tornado. This was followed by an unusual December tornado in the Plains and upper Midwest that produced 99 other tornadoes.

It’s not just December, either: January 2022 saw 124 confirmed proto-tornadoes, making it the third-most tornadoes of the month in records dating back to 1950. Tornadoes killed seven people in Alabama and one person in Georgia during a tornado outbreak that struck the South on January 12.

February has seen a string of deadly tornadoes in recent years, as well as notable outbreaks such as Super Tuesday 2008 and Leap Day 2012.

Fall and winter hurricanes often pose a danger after dark: Another important aspect of severe weather in the fall and winter is the tendency for more tornadoes to occur at night, given fewer hours of daylight in standard time, rather than daytime.

This is important because tornadoes that occur at night are more than twice as likely to be deadly than tornadoes that occur during the day, according to a recent study.

How can you be warned if you are asleep? Here are some tips:

-Purchase a NOAA weather radio. You can find them at most electronics retailers. Warning alerts can be set to sound when any tornado, National Weather Service warning, or severe thunderstorm watch is issued.

– Your smartphone can alert you. Most newer smartphones are capable of receiving wireless emergency alerts from your local NWS office. These include tornado warnings. Make sure your smartphone is sufficiently charged and leave it overnight, and it will emit a special tone and vibrate twice when a tornado warning is issued. However, note that this will not sound for a tornado watch or severe thunderstorm warning.

-Other weather apps can alert you too. Many weather apps, including the Weather Channel, can send alerts to your smartphone, tablet, or smartwatch.

-Know where you are going. Make a plan in advance where you will go.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment, and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.