Crown snow-load is

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

and

hard rime Rime ice forms when supercooled water droplets freeze onto surfaces. In the atmosphere, there are three basic types of rime ice: *Soft rime forms when supercooled water freezes under calm wind conditions. It is milky and crystalline, like suga ...

that accumulates on tree crowns in a cold climate. There are two main climatic conditions in which this phenomenon chiefly takes place. Hard rime is formed when subcooled droplets of

fog Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Reprint from Fog can be considered a type of low-lying cloud usually resembling stratus and is heavily influenc ...

or low-level

stratus cloud Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. The term ''stratus'' describes flat, hazy, featureless clouds at low altit ...

freeze on the

windward In geography and seamanship, windward () and leeward () are directions relative to the wind. Windward is ''upwind'' from the point of reference, i.e., towards the direction from which the wind is coming; leeward is ''downwind'' from the point ...

(wind-facing) side of tree branches, buildings, or any other solid objects. This takes place usually with moderate

wind speed In meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind spe ...

s from and air temperatures between . Snow may accumulate directly on the trees when a

warm front Warm, WARM, or Warmth may refer to: * A somewhat high temperature; heat * Kindness Music Albums * ''Warm'' (Herb Alpert album), 1969 * ''Warm'' (Jeff Tweedy album), 2018 * ''Warm'' (Johnny Mathis album), 1958, and the title song * ''Warm'' ( ...

brings wet snow, the air temperature is slightly above the

freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

and the surface of the tree is colder due to a preceding cold spell. In

Scandinavia Scandinavia is a subregion#Europe, subregion of northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. ''Scandinavia'' most commonly refers to Denmark, Norway, and Sweden. It can sometimes also ...

, largest snow-loads accumulate to the trees on top of medium-sized

fell A fell (from Old Norse ''fell'', ''fjall'', "mountain"Falk and Torp (2006:161).) is a high and barren landscape feature, such as a mountain or Moorland, moor-covered hill. The term is most often employed in Fennoscandia, Iceland, the Isle of M ...

s. The larger fells and mountains have no trees, and the tops of lowest fells do not reach the cloud bases so often. Also the wind speeds are largest on fell tops. One spruce in Northern Finland can collect {{cvt, 3-4, tonne, ton of snow. When the crown is loaded with snow, a storm can easily damage the trees. Snow-loaded trees also pose a risk to powerlines.IF
Insurance company (English)

References

Snow or ice weather phenomena