F0 (weak): 40

72 mph, light damage. F1 (weak): 73-112 mph, moderate damage. F2 (strong): 113-157 mph, considerable damage. F3 (strong): 158-206 mph, severe damage. F4 (violent): 207-260 mph, devastating damage. F5 (violent): 261-318 mph, (rare) incredible damage. All tornadoes, and most other severe local windstorms, are assigned a single number from this scale according to the most intense damage caused by the storm.