By most calculations, September 10 marks the peak of hurricane season in the Atlantic.

The tropics are typically most active around the second week of SeptemberThe tropics are typically most active around the second week of September. —NOAA

Of course, this doesn’t mean that there will be a lot of storms every year on September 10. Sometimes, like this year, the Atlantic is quite quiet during the actual peak.

But it begs the question: Why is early September the peak for hurricanes?

Although average air temperatures have been cooling for about six weeks, the ocean takes much longer to cool. This is because water warms and cools slower than land does. By late August and the first half of September, a lot of heat has built up in the oceans, and hurricanes are nature’s way of moving some of that excess heat from the tropics northward.

Hurricanes begin to form as clusters of thunderstorms over the warm ocean waters of the planet. In the right conditions, these storms can gather together and begin to rotate in an organized cluster. If the winds above these storms aren’t very strong, the rotation can continue, increase, and eventually lead to a tropical storm or hurricane.

Tropical systems originate in the warm waters of the tropics and often move north before being caught in the jet streamTropical systems originate in the warm waters of the tropics and often move north before being caught in the jet stream. —NOAA
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This time of year, the clusters of thunderstorms that are nearly almost always present around the equator have the highest likelihood of developing into an organized storm.

Here in New England, most of our hurricanes have historically hit the area in August and September. Storms have hit in November and June, but those cases are the exceptions. The last hurricane to reach the shores of New England was Bob, back in 1991. During the 25 years since Bob hit, many other storms have wreaked havoc on our shores, but none of them were a hurricane.

The image below shows where hurricanes have hit since 1900.

Hurricanes have struck nearly all parts of the New England coastline over the past centuryHurricanes have struck nearly all parts of the New England coastline over the past century. —NOAA

Since hurricanes must form in the water, it stands to reason that the south coast of New England and Cape Cod have seen the most number of hits, but even the coast of Maine has seen hurricanes.

There are several areas of the Atlantic that may see development in the coming week.

The National Hurricane Center monitors clusters of thunderstorms for potential developmentThe National Hurricane Center monitors clusters of thunderstorms for potential development. —NHC

Over the coming weeks, the waters of the Atlantic and Pacific will begin to cool, and the threat of tropical activity will diminish. The official end of hurricane season is November 30, but storms can and have occurred after that date.