Short Wave

The dangers of warming winter lakes

February 27, 2026

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  • Warming winters are leading to less safe and less predictable lake ice conditions due to increased temperature swings that create weaker ice structures like white ice, which complicates safety assessments. 
  • The loss of reliable lake ice cover threatens cultural traditions, community activities like festivals and ice fishing, and essential infrastructure like winter ice roads in northern communities. 
  • Firefighters, like the Lake Rescue Team in Madison, Wisconsin, are actively training for ice-related emergencies, which are becoming more frequent due to climate change-induced ice instability. 

Segments

Lake Ice Festival Culture
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(00:00:42)
  • Key Takeaway: The Frozen Assets Festival in Madison, Wisconsin, showcases community culture built around frozen Lake Mendota, featuring various ice activities.
  • Summary: Producer Berly McCoy visited the Frozen Assets Festival on Lake Mendota, which hosts activities like hockey, curling, and kite flying on the ice. The festival’s existence relies on the lake freezing sufficiently, which has been threatened in recent years. Organizer James Tai noted that the lake might not freeze at all in the lifetime of current residents under current climate trends.
Black Ice vs. White Ice Safety
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(00:03:33)
  • Key Takeaway: Four inches of clear black ice is safe for walking, whereas white ice, formed from snow or slush, is inherently weaker due to trapped air content.
  • Summary: Scientist Hilary Dugan states that four inches of black ice, which forms directly from freezing lake water, is safe for a person to walk on. White ice, formed from freezing snow or slush, is weaker because it contains more air, making its safe thickness difficult to determine. Fluctuations around freezing temperatures promote the formation of this less safe white ice.
Ice Rescue Training Exercises
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(00:06:08)
  • Key Takeaway: Madison firefighters train for ice rescues using immersion suits and specialized sleds in areas where ice is naturally weak, such as near river inflows.
  • Summary: Firefighter Justin Toos, part of the Lake Rescue Team, demonstrated rescue techniques on Lake Monona near an area of open water. Rescuers wear buoyant ‘Gumby suits’ for protection while practicing maneuvers using rescue sleds and ice-anchored ropes. Ice cracks, often caused by temperature changes or water flow, are identified as common weak points where falls occur.
Dangers of Freeze-Thaw Cycles
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(00:09:02)
  • Key Takeaway: Multiple freezes and thaws create dangerous false ice shelves—a layer of ice over water on top of solid ice—which significantly increases the risk of unexpected breakthroughs.
  • Summary: Justin Toos explained that the previous year was busy for rescues due to mild winters causing multiple freeze-thaw events. These events create a dangerous structure where a new layer of ice forms over water sitting on top of older ice, leading to falls even when the surface appears solid. A person in one such incident was trapped in the water for about 25 minutes before rescue.
Global Ice Loss Statistics
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(00:10:12)
  • Key Takeaway: Half of the documented fatal drownings through ice between 1991 and 2017 are correlated with warmer winter air temperatures, and 5,700 lakes may become permanently ice-free this century.
  • Summary: Global change biologist Sapna Sharma documented over 4,000 fatal drownings related to ice breakthroughs across 10 countries from 1991 to 2017, with 50% linked to air temperature. ‘Winter weirding’—intense swings between cold and heat—destabilizes ice, making it harder to judge safety. Projections suggest 10 to 28 fewer days of ice cover by century’s end under current emission scenarios.