Record August Rainfall and Hurricanes

Some interesting numbers popped off the page as I was scanning the August rainfall records for Baltimore. The August 12 record is 4.91 inches set back in 1955. It struck me that this must have been related to tropical weather and further digging revealed that Hurricane Connie was making landfall in the Carolinas on that date. Rain bands ahead of the storm were likely responsible for the record.

Additional research showed that the Mid Atlantic region was hit by the remnants of Hurricane Diane 5 days later with additional rains falling on the already saturated ground. The combination of the two storms plus other rains brought the August monthly rain total to 18.35 inches, the record for the month and the most rain recorded in any month in Baltimore.

Baltimore’s Top 5 Wettest Months
18.35” August 1955
13.83” August 1933
12.41” September 1934
12.28” August 1911
11.50” September 1999

Notice that the biggest rains fall in the busiest hurricane months of August and September and three of the five months were in the first half of the 20th century.

Below is information taken from NOAA archives on hurricanes Connie and Diane.


Connie was first detected as a tropical storm over the tropical Atlantic on August 3. It moved just north of west for several days, reaching hurricane strength several hundred miles northeast of the Leeward Islands on the 5th. After passing north of the Leewards on the 6th, Connie turned northwestward – a motion that continued until the 10th. An erratic, generally north-northwestward motion then brought Connie to the North Carolina coast on August 12 as a Category 3 hurricane. This was followed by a gradual northwestward turn through August 14, when Connie dissipated over the eastern Great Lakes.

Fort Macon, North Carolina reported 75 mph sustained winds with gusts to 100 mph, while a storm surge of up to 8 ft occurred along the coast. There were no reported deaths and the damage in the United States was $40 million. However, the most significant aspect of Connie was the rainfall of up to 12 inches that affected the northeastern United States.

The rainfall map above for Hurricane Connie was constructed using rainfall data from the National Climatic Data Center in Asheville, North Carolina.

Diane was first detected over the tropical Atlantic on August 7. Moving generally west-northwestward, the cyclone became a tropical storm on the 9th. Diane became a hurricane on August 11, by which time it was moving northwestward. A northward turn occurred on the 12th, followed by a westward turn on the 13th and a west-northwestward motion on the 14th. This motion brought Diane to the North Carolina coast on August 17 as a Category 1 hurricane. The storm turned northward across Virginia, then it turned northeastward and moved back into the Atlantic near Long Island, New York on August 19. Diane became extratropical over the North Atlantic on the 21st.

The rainfall map above for Hurricane Diane was constructed by Paul Kocin for the National Weather Service.


Five named storms have developed in the Atlantic/Caribbean/Gulf basins so far this hurricane season. The window for peak activity is just opening up and it will be interesting to see how things play out. Check our Hurricane Tracker page for the latest tropical developments…..

John Collins


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