<P> The Atlantic hurricane season is the period in a year when hurricanes usually form in the Atlantic Ocean . Tropical cyclones in the North Atlantic are called hurricanes, tropical storms, or tropical depressions . In addition, there have been several storms over the years that have not been fully tropical and are categorized as subtropical depressions and subtropical storms . Even though subtropical storms and subtropical depressions are not technically as strong as tropical cyclones, the damages can still be devastating . </P> <P> Worldwide, tropical cyclone activity peaks in late summer, when the difference between temperatures aloft and sea surface temperatures is the greatest . However, each particular basin has its own seasonal patterns . On a worldwide scale, May is the least active month, while September is the most active . In the Northern Atlantic Ocean, a distinct hurricane season occurs from June 1 to November 30, sharply peaking from late August through September; the season's climatological peak of activity occurs around September 10 each season . This is the norm, but in 1938, the Atlantic hurricane season started as early as January 3 . </P> <P> Tropical disturbances that reach tropical storm intensity are named from a pre-determined list . On average, 10.1 named storms occur each season, with an average of 5.9 becoming hurricanes and 2.5 becoming major hurricanes (Category 3 or greater). The most active season was 2005, during which 28 tropical cyclones formed, of which a record 15 became hurricanes . The least active season was 1914, with only one known tropical cyclone developing during that year . The Atlantic hurricane season is a time when most tropical cyclones are expected to develop across the northern Atlantic Ocean . It is currently defined as the time frame from June 1 through November 30, though in the past the season was defined as a shorter time frame . During the season, regular tropical weather outlooks are issued by the National Hurricane Center, and coordination between the Weather Prediction Center and National Hurricane Center occurs for systems which have not formed yet, but could develop during the next three to seven days . </P> <P> The basic concept of a hurricane season began during 1935, when dedicated wire circuits known as hurricane circuits began to be set up along the Gulf and Atlantic coasts, a process completed by 1955 . It was originally the time frame when the tropics were monitored routinely for tropical cyclone activity, and was originally defined as from June 15 through October 31 . Over the years, the beginning date was shifted back to June 1, while the end date was shifted to November 15, before settling at November 30 by 1965 . This was when hurricane reconnaissance planes were sent out to fly across the Atlantic and Gulf of Mexico on a routine basis to look for potential tropical cyclones, in the years before the continuous weather satellite era . Since regular satellite surveillance began, hurricane hunter aircraft fly only into storm areas which are first spotted by satellite imagery . </P>

When does hurricane season begin in the united states