Tropical Storm Lee was the thirteenth named storm and fifteenth system overall of the 2011 Atlantic hurricane season, developing from a broad tropical disturbance over the Gulf on September 2. It was designated as Tropical Storm Lee the next day. Prior to 2020, when Marco formed on August 22, Lee was tied with 2005's Maria as the earliest-forming 13th Atlantic tropical storm. The system was rather large, and due to drifting, Lee brought flash flooding to the Gulf Coast. Flooding associated with the rains caused significant property damage in the areas, with drowning deaths reported in both Mississippi and Georgia. Elsewhere, the storm helped spread wildfires that destroyed homes and killed two people in Texas, and a traffic accident in Alabama resulted in one death. Rough surf offshore drowned one person in each of these states. After becoming extratropical, Lee caused historic flooding in Pennsylvania, New York, and Canada, mainly Quebec and Ontario.

The 2011 Atlantic hurricane season was the second in a group of three very active Atlantic hurricane seasons, each with 19 named storms, only behind 1887, 1995, 2010, and 2012. The above-average activity was mostly due to a La Niña that persisted during the previous year. Of the season's 19 tropical storms, only seven strengthened into hurricanes, and four of those became major hurricanes: Irene, Katia, Ophelia, and Rina. The season officially began on June 1 and ended on November 30, dates which conventionally delimit the period during each year in which most tropical cyclones develop in the Atlantic Ocean. However, the first tropical storm of the season, Arlene, did not develop until nearly a month later. The final system, Tropical Storm Sean, dissipated over the open Atlantic on November 11.