Tropical Storm Heidi was the last of the four tropical systems to develop from the extended surface trough of low pressure, forming on September 11 northeast of the Bahamas and intensifying into a tropical storm the next day. After initially moving to the northwest, Heidi curved northeastward and attained its peak intensity of 65 mph (100 km/h) on September 14 off the coast of Virginia. The storm failed to become a well-organized system, and it gradually weakened while accelerating north-northeastward.