The Teton-Yellowstone tornado was a rare high-altitude tornado that occurred on July 21, 1987. Peaking at EF-4 strength, it is the strongest tornado ever recorded in the state of Wyoming.

The tornado traveled 24 miles and carved an incredible 1.5-mile-wide path through the Teton Wilderness and Yellowstone National Park, even crossing the Continental Divide. The tornado spawned from a mesocyclone, the center of which passed almost right alongside the tornado path.

No fatalities or injuries were reported, but up to a million trees were uprooted by the storm. Nine campers in the Bridger-Teton National Forest were among the handful of witnesses, describing a fast-moving train-like noise and golf-ball hail, but no funnel cloud. The EF-4 rating was based on severe tree damage and assigned by Dr. Tetsuya Theodore Fujita, the man who invented the tornado scale that is named after him and still in use today. Many trees were flattened, with many more stripped of leaves and limbs with the trunks debarked.

Winds in an EF-4 tornado are measured between 207 and 260 mph, numbers rarely experienced in the Rocky Mountains. The damage occurred at elevations between 8,500 and 10,000 feet, making it one of the highest altitude violent tornadoes ever recorded in the U.S.

Unfortunately, this rare event was unable to be studied further, as the Yellowstone Fires of 1988 quickly destroyed the evidence. Fujita himself described the damage from this tornado only being comparable to the 1974 Super Outbreak and the April 1977 Birmingham Tornado, putting this extremely rare event among famous company.

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On This Day in 1987: Teton-Yellowstone Rare Tornado