What is the average wind speed inside a tornado?

The Fujita-Pearson scale ranks tornadoes by wind speed. The rankings range from F0 (very weak) to F6 (inconceivable). F0 denotes wind speeds of 40 to 72 mph; F1, 73 to 112 mph; F2, 113 to 157 mph; F3, 158 to 206 mph; F4, 207 to 260 mph; F5, 261 to 318 mph; and F6, 319 to 379 mph.