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5 weather threats to be wary of during the fall

By Kevin Byrne, AccuWeather staff writer
October 12, 2017, 8:50:35 AM EDT

While the autumn season may be best known for brilliant views of changing foliage and a heavy dose of pumpkin, there are many weather threats that should be anticipated during the fall.

From early signs of winter to tropical development, people should prepare for a wide variety of different weather phenomena that occur during the fall season. Several of which can be notably dangerous.

Here are five weather threats to watch out for this season:

Severe weather ramps up in a secondary peak


Dangerous tornado on the Plains. (Photo/David Schliepp/iStock/Thinkstock)

Like in the spring, the fall is a changing season with an increase in the clash between cold, dry air and warm, humid air. This clash of air masses can help spawn the development of severe thunderstorms.

"The peak is not as strong in the spring, primarily because there’s not as much heat and humidity around during this part of the year," AccuWeather Senior Meteorologist Andy Mussoline said.

The secondary peak of severe weather typically lasts from October into November, he added.

There is a smaller number of tornadoes on average across the country during October and November, compared to April and May, according to the National Climatic Data Center (NCDC).

Based on an averaging period from 1991-2010, the NCDC reports that 155 tornadoes form during April, while a whopping 276 occur in May. That number drops to 61 in October and 58 in November. Still, while the number isn't as large, it's important that people are always prepared for a severe weather event.

Severe storms can encompass areas from from the Plains to the Ohio Valley and Southeast, because it's easier for warm and humid air to reach those areas. The threat can also reach the Northeast, but it's not as high, because the region is farther removed from widespread heat and humidity, Mussoline said.

Fog can dangerously reduce visibility


Rural road with headlights of car appearing through the fog. (Photo/AnnElizabethPhotography/iStock/Thinkstock)

Fog can severely impact the visibility for motorists, which can increase accident risk and lead to travel delays. On average, more than 28,500 vehicles crashes occur in the United States each year due to fog, according to the Federal Highway Administration (FHWA).

Fog is also a frequent disruptor of air travel, forcing many airlines to delay flights until conditions improve. While fog is not strictly limited to the fall season, it does tend to increase this time of year.

“There is a significant increase in fog events during the fall primarily due to longer and cooler nights,” Mussoline said. “Fog typically develops during the overnight hours and lasts into the early- to mid-morning hours.”

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Early frosts can damage plants


Frost can bring an abrupt and unwanted end to the growing season for sensitive plants.

"The most susceptible areas to early season frosts are rural areas; suburban areas can provide better protection to any early season intrusions of cold air," Mussoline said.

The pavement is typically warm inside most cities, and this can prevent early frost from occurring, but out in more rural areas, pavement is not as prevalent.

Early-season snowstorms can knock out power


Autumn and winter collided in parts of Colorado on Friday, Sept 23, 2016. (Photo/La Plata County Sheriff's Office)

Snow that falls during autumn can be heavy and wet instead of light and powdery. With more leaves that haven't fallen, there is more of a surface area for the snow to accumulate on the trees.

This adds more more weight to the trees, meaning they could be more susceptible to snapping or having branches fall off, according to Mussoline. This can cause damage when trees topple onto cars or homes. It can also mean travel delays when they fall onto roadways, or power outages when they drop onto power lines.

Twenty-four percent of weather-related crashes each year occur on snowy, slushy or icy pavement and 15 percent occur during snowfall or sleet, according to the FHWA.

Hurricane season continues until Nov. 30


This home on Staten Island, New York, was left severely damaged by Hurricane Sandy. (FEMA Photo by Andrea Booher - Dec 19, 2012)

The Atlantic hurricane season begins in June, and even though the peak occurs on Sept. 10, the Atlantic Basin can remain quite active up until the very end of November, when the season concludes.

A key factor in why tropical cyclones can develop so late in the year is that sea surface temperatures remain warm enough. The ideal temperatures for tropical development are in the upper 20s to 30 degrees Celsius (80-86 degrees Fahrenheit), according to AccuWeather Senior Meteorologist Jim Andrews.

Even if parts of the Atlantic begin to cool, there are areas close to the equator, such as in the Caribbean, that remain warm enough for tropical activity to occur well into the fall, Andrews said.

There have been several destructive storms that have caused hardship to millions during the latter part of the season, including most recently, Hurricane Matthew. These systems show why it's important for people along the Gulf and East coasts to remain prepared all the way through Nov. 30.

Here are three of the most notorious late-season storms to impact the U.S.:

late season hurricanes

Have questions, comments, or a story to share? Email Kevin Byrne at, follow him on Twitter at @Accu_Kevin. Follow us @breakingweather, or on Facebook

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