Tropical Storm Dorothy was the deadliest tropical cyclone of the 1970 Atlantic hurricane season. The fourth named storm and fifth tropical storm or hurricane of the season, Dorothy developed on August 17 from a tropical wave to the east of the Lesser Antilles. It tracked west-northwestward throughout its entire duration, and despite forecasts of attaining hurricane status, Dorothy reached peak winds of 70 mph (110 km/) – slightly below hurricane status. The storm struck Martinique on August 20, and subsequently began a gradual weakening trend in the Caribbean Sea. On August 23, Dorothy dissipated south of Hispaniola.

The 1970 Atlantic hurricane season officially began on June 1 and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The season was fairly average, with 14 named storms forming, of which seven were hurricanes. Two of those seven became major hurricanes, which are Category 3 or higher on the Saffir–Simpson scale. Also, this was the first season in which reconnaissance aircraft flew into all four quadrants of a tropical cyclone.