An F3 tornado is a powerful tornado with wind speeds capable of causing severe structural damage. On the original Fujita Scale, an F3 carried estimated winds of 158 to 206 mph. On the Enhanced Fujita Scale used today, the equivalent rating (EF3) corresponds to winds of 136 to 165 mph. The lower numbers don’t mean the tornadoes got weaker. Engineers determined that the wind speeds needed to cause that level of destruction were lower than originally believed.
How the Rating Scale Works
Tornadoes aren’t rated by measuring their wind speed directly. Instead, trained National Weather Service personnel survey the damage after the storm passes and work backward to estimate how fast the winds must have been. The NWS is the only federal agency authorized to assign official tornado ratings.
Surveyors use 28 specific “damage indicators,” which are types of structures and objects like homes, commercial buildings, trees, and power lines. For each one, they match the observed destruction to one of eight degrees of damage, then estimate whether the wind speed falls toward the upper or lower end of the expected range. They repeat this process across multiple structures along the tornado’s path before settling on a final rating. The rating reflects the highest wind speed that occurred anywhere along the path, not the average.
Original F3 vs. Modern EF3
The original Fujita Scale was introduced in 1971 and used broad wind speed estimates based on the engineering knowledge available at the time. An F3 tornado on that scale had estimated winds of 158 to 206 mph. In 2007, the Enhanced Fujita Scale replaced it, incorporating decades of new research into how buildings actually fail under wind loads. That research showed the wind speeds necessary to cause “F3-level” damage were not as high as once thought, so the EF3 range was adjusted downward to 136 to 165 mph.
If you see an older tornado described as an F3, it was rated on the original scale. Anything rated after February 2007 uses the EF designation. The level of destruction is comparable between the two. The numbers just got more accurate.
What EF3 Damage Looks Like
EF3 tornadoes cause severe damage. Entire stories of well-built homes can be destroyed, with exterior and interior walls collapsed. Roofs are torn completely off. Large trees are uprooted or snapped, and significant sections of power infrastructure are brought down. Cars and heavy objects can be thrown considerable distances.
A real-world example: in November 2017, an EF3 tornado touched down northeast of Eaton, Indiana, and traveled 39 miles to the northeast before lifting near Celina, Ohio. It stayed a quarter to a third of a mile wide for most of its 66-minute life span, causing moderate to major damage to numerous farms along with substantial tree and power line destruction. That combination of path length, width, and duration is characteristic of a strong EF3. These are not brief, narrow funnels. They can carve long swaths of damage across entire counties.
How Common Are They?
EF3 tornadoes are uncommon but not rare. Roughly 4 percent of all recorded tornadoes in the United States have been rated F3 or EF3. For perspective, about 80 percent of tornadoes are weak (EF0 or EF1), another 14 percent are EF2, and less than 1 percent reach EF4 or EF5. So an EF3 sits at the boundary between “strong” and “violent,” powerful enough to destroy solidly built houses but not quite at the catastrophic level of the strongest tornadoes on record.
In a typical year, dozens of EF3 tornadoes occur across the country, mostly concentrated in the spring and early summer months across the central United States. They can happen in any month, though. The 2017 Indiana tornado mentioned above struck in November.
Surviving EF3 Winds
Standard residential construction is not designed to withstand EF3 winds. Most building codes in the U.S. only require homes and commercial buildings to resist winds up to about EF2 intensity. That means an EF3 tornado can cause catastrophic failure in ordinary houses, tearing away roofs, collapsing walls, and in some cases leveling the structure entirely.
Purpose-built storm shelters are a different story. Shelters constructed to the ICC 500 standard, a national design specification for storm shelters, provide what engineers call “near-absolute life safety” from tornadoes up to and including EF5. Hundreds of these shelters have been directly hit by tornadoes, and none have failed. These can be standalone safe rooms, reinforced interior rooms, or community shelters in schools and public buildings.
Mobile homes offer virtually no protection. In the November 2002 Van Wert, Ohio, tornado (which fluctuated between F3 and F4 strength along its 53-mile path), two fatalities occurred when the tornado destroyed a mobile home near Continental, Ohio. Another person died when winds swept a car off the road. If you’re in a mobile home or vehicle during an EF3 tornado, you’re in extreme danger. A basement, storm shelter, or the lowest interior room of a solidly built structure is the safest place to be.