Bear Lake, a vast body of water straddling the border of Utah and Idaho at an elevation of nearly 5,925 feet, is famous for its stunning turquoise color. A complete, solid freeze of this high-altitude lake is a surprisingly rare event. The lake’s massive size and unique physical properties work against the formation of a full ice sheet, even when surrounding winter temperatures are frigid.
The Historical Rarity of Complete Freezing
The complete freezing of Bear Lake’s surface is an infrequent occurrence, a fact that has become more pronounced in recent decades. Over the past century, the lake has been documented to freeze over about two-thirds of the time, an average that has significantly decreased. For example, from 1995 to 2019, the lake froze completely in less than half of those years, demonstrating a clear trend toward less frequent ice cover.
Most winters see ice forming along the shorelines and in shallow bays, but the entire 109-square-mile surface rarely locks up. A recent complete freeze occurred in 2016, lasting 84 consecutive days from January through March. The lake also froze completely in February 2022, the first full freeze observed in five years, highlighting the event’s irregularity.
Geographic and Physical Reasons Bear Lake Resists Freezing
The primary reason Bear Lake resists freezing is its immense volume, which acts as a thermal buffer against cold air. With a maximum depth of 208 feet and an average depth of 94 feet, the lake holds a huge mass of water that must cool down significantly before ice can form. This water must drop to its maximum density temperature of about 39°F (4°C) from top to bottom, a process known as “overturn,” requiring a prolonged period of intense, sustained cold.
Wind exposure at its high elevation is another factor preventing ice formation. The wide, open expanse is constantly subjected to strong westerly winds, which vigorously churn the water surface. This wind action continuously mixes the colder surface water with warmer layers below, preventing the top layer from remaining still long enough to reach the freezing point of 32°F (0°C). The movement transfers heat from the depths to the surface, making it difficult for a stable ice sheet to establish itself.
The lake’s unique water chemistry contributes to its character. Its famous moniker, the “Caribbean of the Rockies,” comes from the vivid turquoise color caused by microscopic particles of calcium carbonate suspended in the water. These particles reflect light, giving the lake its distinct hue.
Winter Ice Formation and Safety Zones
While the main body of the lake often remains open, ice reliably forms in specific, shallower locations. Sheltered coves and areas near the shoreline are the first to develop a stable ice layer because they lack the depth and wind exposure of the central lake. Anglers often take advantage of these areas to fish through the ice for the endemic Bonneville cisco, a unique winter activity involving scooping the fish with dip nets.
Ice on a body of water as large as Bear Lake requires caution due to variable and unpredictable thickness. Large, deep lakes can have hidden springs and currents that create thin spots, even when the rest of the ice appears solid. Local park officials advise that no ice should ever be considered completely safe, as thickness can change dramatically within a few feet.
For walking, a minimum of four inches of clear, new ice is recommended, and more for snowmobiles or small ATVs. Visitors should always check with local authorities for current conditions, as the ice over Bear Lake is inconsistent due to its depth and subsurface geothermal activity.