When describing gentle winter precipitation, people use various terms, but meteorology applies specific classifications to distinguish between types of snowfall. This precise terminology is used by weather services and forecasters to communicate expected conditions and impacts accurately. Understanding the difference between light snow, a snow flurry, and other granular forms helps clarify what to expect. These distinctions rely on the precipitation’s intensity, duration, and the physical structure of the ice particles.
Meteorological Definitions of Snow Intensity
The official classification of light snow is based on two measurable factors: horizontal visibility and the rate of precipitation. Meteorological services, such as the National Weather Service (NWS), use these criteria to categorize snowfall intensity as light, moderate, or heavy. This standard definition removes the subjectivity of personal observation, allowing for consistent reporting.
Snowfall is classified as “light snow” when visibility is restricted but remains greater than 5/8 of a statute mile (approximately one kilometer). This means objects more than half a mile away are still discernable, even though the air is visibly filled with falling flakes.
In terms of liquid equivalent, light snow is defined as having a precipitation rate of less than 1.0 millimeter per hour. This low rate differentiates it from moderate snow, which typically ranges from 1.0 to 2.5 millimeters of liquid equivalent per hour. Continuous snowfall must meet both the visibility and the precipitation rate criteria to be classified as light.
Common Terms for Light Snowfall
Outside of formal meteorological reports, the most common term for gentle snowfall is a “snow flurry.” Snow flurries are transient and intermittent, often falling for short durations with little or no accumulation expected. They consist of small, scattered snowflakes originating from cumulus clouds, which are less extensive than the stratus clouds that produce continuous snow.
The term “dusting” describes the result of extremely light snowfall. A dusting refers to the accumulation itself: a thin, barely noticeable layer of snow on the ground or surfaces. While a flurry describes the falling precipitation, a dusting describes the minimal layer left behind. Flurries typically produce a dusting, but continuous light snow can also result in the same negligible accumulation.
Related Granular Snow Forms
Precipitation that appears to be light snow may be a different form of frozen water. One distinct type is “snow grains,” which are opaque white particles of ice. These particles are flat or elongated and are typically less than 1 millimeter in diameter. Snow grains are the solid equivalent of drizzle and do not produce significant accumulation.
Another phenomenon is the fall of “ice crystals,” sometimes called “diamond dust.” This precipitation consists of minute ice crystals that remain suspended in the air and fall slowly. Ice crystals are distinguished from snowflakes because they are single, isolated crystals, not aggregates. Their presence can cause a shimmering effect in the air, especially under sunlight.