The winds inside a tornado can range from as little as 70 to an estimated 300 miles per hour, the fastest weather-related wind speed found on earth. The only faster winds that I've been able to identify are those generated by the blast of a volcano (Mt. St. Helens, for example, is estimated to have produced winds of about 680 miles per hour. By comparison, a hurricane's top winds are thought to be around 200 mph.
---David Murphy