Official Start of Hurricane Season Is Less Than a Week Away; Here’s What's Typical in June

The National Hurricane Center selected the June 1 to Nov. 30 period for the Atlantic hurricane season because it encompass more than 97% of tropical cyclones. But as this year showed, there's a reason those dates only account for 97% of storms; Tropical Storm Arthur made a brief appearance off the southeastern coast of the United States May 16-19.

(MORE: What the Most Active Atlantic Hurricane Seasons Have Delivered in June, or Earlier)

Early in the season, we typically do not look at the main development region of the central and eastern Atlantic for tropical storms or hurricanes. We look closer to home.

The southeastern U.S. coast, the Gulf of Mexico and the western Caribbean Sea are breeding grounds for tropical cyclones during June. July is when we start to look a bit farther east because the region of the Atlantic near the Lesser Antilles can also become more ripe for development.

The Cape Verde season, when tropical storms and hurricanes tend to form more often in the central or eastern Atlantic Ocean from disturbances moving off the northwestern coast of Africa, generally doesn't begin until early August.

Since storms that form early in the year typically start out closer to land, that can increase the chance of impacts along the Gulf and Southeast coasts of the U.S., as well as parts of the Caribbean.

Early-Season Activity Is Typically Slow

Just 13% of the tropical storms since 1851 in the Atlantic have occurred in June and July combined. For comparison, August, September and October have accounted for 24%, 36% and 21% of all tropical storms on record, respectively.

Hurricanes are even rarer, with just 33 of them documented in June and 58 in July. July 2018 was a rarity for the Atlantic, with two hurricanes forming in the month: Beryl and Chris. Two or more hurricanes forming in July has only happened six other times since satellite observations began in 1966.

It's Not Too Early for Major Impacts

Hurricane Audrey is the strongest U.S. landfalling hurricane in June. It roared ashore in Cameron Parish, Louisiana, as a Category 4 on June 27, 1957.

But it doesn't take an early-season hurricane in June to cause significant impacts.

Take Tropical Storm Allison in June 2001. Allison made landfall as a low-end 50-mph tropical storm near Freeport, Texas, and quickly weakened to a tropical depression. The remnants of Allison meandered and lingered for days, allowing a slow-moving rainband associated with it to flare up and unleash epic amounts of rainfall in the Houston metro area, resulting in severe flooding.

In June 1972, Hurricane Agnes made landfall in Florida, but its legacy is more strongly linked to its second wind as a tropical storm, when it curled northwestward toward New York City and stalled over the Northeast, producing flooding rainfall in the interior Northeast.

Last year, Barry became the most recent hurricane to make a U.S. landfall in July, when it caused flooding from Louisiana to Arkansas. Five years earlier, in 2014, Arthur made a U.S. landfall in July, raking eastern North Carolina and the Outer Banks with storm-surge flooding and strong winds.

Dolly (2008), Cindy (2005) and Dennis (2005) are the only other three hurricanes to make a U.S. landfall during July in the past 15 years.

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