The Atlantic hurricane season officially began on June 1, 1972. Although 19 tropical cyclones developed, only seven of were named, below the 1950-2000 average of 9.6 named storms per season. Of the seven tropical or subtropical storms, three of them strengthened into a hurricane, which is also below average. None of the three hurricane became major hurricanes, which is Category 3 or greater on the Saffir–Simpson hurricane wind scale. Overall, the season was inactive, despite having a similar number of tropical waves as the previous season. The lack of activity was attributed to an El Niño – which causes below normal sea surface temperatures over the eastern Atlantic – and strong vertical wind shear. One subtropical storm and two hurricanes made landfall during the season and caused at least 137 fatalities and more than $2.1 billion in damage. The last storm of the season, Subtropical Storm Delta, became extratropical on November 7, about 23 days before the official end of hurricane season on November 30.