Metal Tornado

Although it's mentioned by any character, a tornado is measured by its destructive force with the Fujita's Scale. It was named after Tetsuya Fujita, who in 1971 in collaboration with Allan Pearson created a scale to differentiate a twister according the wind speed:

F0: 60-117 km/h or 45-72 mph (light damage).

F1: 117-181 km/h or 73-112 mph (moderate damage).

F2: 181-250 km/h or 113-157 mph (significant damage).

F3: 250-320 km/h or 158-206 mph (severe damage).

F4: 320-420 km/h or 207-260 mph (devastating damage).

F5: 420-510 km/h or 261-308 mph (incredible damage).

F6: 510-610 km/h or 309-379 mph (altough initially Fujita scale have five marks, in 1999 a tornado located in Bridge CreekMoore, Oklahoma, devastated with a force more powerful never seen before. It was the only one F6 registered in history, despite The United States National Weather Service officially maintains that the Bridge Creek-Moore tornado was a F5, not F6).

The "$" on the coffee sign at the gas station follows the number rather than preceding it. This is not how monetary amounts are written in Pennsylvania (where the story supposedly takes place), but is true in Quebec (where the movie was filmed).

References Reba (2001)