National Weather Service officials say the Wednesday twister had an estimated peak wind speed of 160 mph when it slammed into Adairsville, about 60 miles northwest of Atlanta.
Crews that toured the destruction Thursday rated the tornado, which destroyed more than 60 buildings in Bartow and Gordon counties, as a strong EF3 twister.
The heaviest damage was found at the Daiki Corp. manufacturing plant in Adairsville, where the 160 mph winds struck. That is just shy of an EF4 tornado, which has winds of 166 mph and above.
The tornado killed an Adairsville man and injured 17 people.