F1 tornado in Glenn County, California

What F1 means. This tornado was rated on Fujita’s original scale, used until 2007. F1 meant moderate damage: roofs badly stripped, mobile homes pushed off foundations or overturned, windows broken; the scale paired it with winds of 73–112 mph, figures later judged too high, especially toward the top of the scale, and revised downward in the Enhanced Fujita scale. Ratings then, as now, came from the damage.