What are the swirling, ghostly vortices that dance above freezing lakes and hot springs?

Nature · Published 3 October 2026 Swipe more like this →

In short: Known as steam devils, these rare, short-lived whirlwinds form when cold, dry air rushes over warm water. Unlike powerful tornadoes, these gentle vortices draw up fog to become visible. They are a fascinating, overlooked mechanism for transporting moisture and heat from the surface into the atmosphere above.

First identified by researchers Lyons and Pease in 1972 following observations on Lake Michigan, steam devils are distinct from the more destructive waterspouts. While waterspouts are essentially tornadoes over water, steam devils are smaller, weaker, and rely on specific temperature gradients. They typically form during cold air outbreaks when a brisk wind—at least 3.2 km/h—blows across an unfrozen body of water. This interaction creates arctic steam fog, which rises and condenses into streamers before being pulled into a rotating vortex.

These phenomena are not limited to frigid northern lakes. They also appear frequently in geyser basins, such as those in Yellowstone Park, where high water temperatures allow them to form even in mild weather. In 1982, observers documented a cluster of seventeen steam devils at a Yellowstone site where the air temperature was between 17 and 21 °C, yet the extreme heat of the water maintained the necessary thermal instability. These smaller geyser-basin devils can rotate at speeds of around 60 rpm, significantly faster than the sluggish, few-rotations-per-minute motion often seen in their larger lake-based counterparts.

Beyond their visual intrigue, steam devils may play a significant role in atmospheric dynamics. Airborne radar studies suggest that they can penetrate the thermal internal boundary layer, potentially acting as a more efficient mechanism for vertical moisture transport than normal convection. By joining the layer of steam fog near the surface to cumulus clouds above, they serve as a bridge in the convective structure of the atmosphere. Though they rarely last more than a few minutes, these vortices highlight the complex, invisible work of heat exchange occurring constantly between our water bodies and the air.

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