How the EF Scale Works
Tornadoes are rated after they happen, not during. NWS survey teams examine the damage path and use 28 different Damage Indicators (buildings, trees, towers, etc.) to estimate the wind speed that caused the destruction. The tornado then gets an EF rating based on the highest estimated wind speed anywhere along its path.
This means a tornado's EF rating is a measure of what it did, not necessarily what its peak winds were at every moment. A tornado in open farmland may cause EF1-level damage even if its actual winds were stronger — there simply wasn't enough to damage to rate it higher.
The Ratings
EF0 — 65–85 mph
Light damage. Broken tree branches, shallow-rooted trees pushed over, damage to gutters and siding. Most tornadoes in the US are EF0.
EF1 — 86–110 mph
Moderate damage. Mobile homes overturned or destroyed. Roofs stripped, garage doors pushed in, large trees snapped. Moving vehicles pushed off roads.
EF2 — 111–135 mph
Considerable damage. Roofs torn off well-built homes. Mobile homes demolished. Large trees uprooted. Freight cars overturned. Objects become dangerous missiles.
EF3 — 136–165 mph
Severe damage. Entire stories of well-built houses destroyed. Heavy cars lifted and thrown. Structures with weak foundations blown away. Trees debarked.
EF4 — 166–200 mph
Devastating damage. Well-built homes completely leveled. Cars thrown long distances. Large structures sustain severe damage. These are rare — about 1% of all tornadoes.
EF5 — Over 200 mph
Incredible damage. Strong-frame houses swept clean off their foundations. Steel-reinforced concrete structures critically damaged. High-rise buildings sustain severe structural damage. Extremely rare — fewer than 1 per year on average.
Key Facts
Most Are Weak
About 77% of all tornadoes are EF0 or EF1. Only about 0.1% reach EF5.
Rated After the Fact
The NWS sends survey teams to examine damage. Ratings are assigned hours or days after the tornado, not during it.
Damage, Not Wind
The EF scale is based on damage indicators, not direct wind measurement. A tornado over open fields may appear weaker than it actually was.
Replaced the F-Scale in 2007
The Enhanced Fujita Scale improved on the original by using more damage indicators and better accounting for construction quality.
The 28 Damage Indicators
Rather than relying on a single building type, the EF scale uses 28 different Damage Indicators — categories like one- and two-family homes, mobile homes, strip malls, schools, hardwood trees, softwood trees, and utility poles — each with its own set of Degrees of Damage describing what a given wind speed would do to that specific structure. A survey team matches what they actually find in the field to the closest damage description, which is far more accurate than the original Fujita Scale's simpler, more subjective damage categories from the 1970s. This is also why two tornadoes with identical peak winds can receive different ratings, if one passed through a well-built subdivision and the other crossed open farmland with few structures to damage.
Frequently Asked Questions
Can a tornado's rating change after it's initially announced?
Yes. Initial ratings from early damage reports are sometimes revised once the full survey is complete and every damage indicator along the path has been assessed.
Does a higher EF rating always mean more deaths?
Not necessarily — an EF5 over open land can cause zero deaths, while a weaker EF1 through a mobile home park or densely populated area can be far deadlier. Rating measures damage intensity, not casualty count.
What's the strongest tornado ever recorded?
The 2013 El Reno, Oklahoma tornado was measured by mobile radar at over 295 mph in the air, though it was officially rated EF3 based on ground damage, since it crossed mostly open terrain with few structures to register the full intensity.
How long does it take to get an official EF rating after a tornado?
Local NWS survey teams typically complete their assessment and issue a preliminary rating within a day or two, though a full, detailed report can take longer for large or unusually complex damage paths.
How to Get Tornado Alerts
StormCast delivers every NWS tornado warning, watch, and emergency directly to your Android phone within moments of being issued — before you even hear the sirens. The app checks the NWS feed every 30 seconds.
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A note on this guide: Thresholds and criteria described here are general and can vary by NWS forecast office, region, and over time. This content is educational — always check your local National Weather Service office for the specific criteria that apply to your area.