A tornado's strength cannot be determined by just looking at it. Examining the damage will give you a better idea of the strength of the tornado. This is where the enhanced fujita scale comes in.
EF scale gives an accurate indication of tornado strength which includes 28 damage indicators such as building type, structures and trees, plus eight degrees of damage giving more detailed analysis and better correlation between damage and wind speed.
The scale goes from EF 0, the weakest, to EF 5 which is the strongest. EF 0 to EF 1 twisters cause minor to moderate damage from branches being broken off trees and roof shingles being pulled off to mobile homes overturned and windows broken out.
When tornadoes reach EF 2 and EF 3, strength the damage becomes more severe with roofs being torn off, mobile homes destroyed, large trees being snapped in half and entire stories of houses destroyed.
Winds begin to reach 166 miles per hour and stronger with EF 4 and EF 5 tornadoes. This is when houses are completely destroyed and cars are thrown hundreds of feet.
Only .8 percent of tornadoes are classified EF 4 or stronger. However, they are the most deadly. 67 percent of tornado fatalities come from these violent swirling wind machines.