Snow is a type of precipitation that occurs when the atmospheric temperature is at or below freezing, specifically at $0$ degrees Celsius or $32$ degrees Fahrenheit, and there is an adequate amount of moisture in the air. The formation of snow begins high in the atmosphere, where temperatures are cooler. In this colder region, water vapor condenses, leading to the creation of tiny ice crystals. As these ice crystals descend toward the ground, they aggregate to form snowflakes. If the temperature remains at or below freezing during their descent, the snowflakes will reach the ground as snow.

Two primary factors influence the formation of snow: temperature and moisture. The temperature must be sufficiently low to facilitate the freezing of water vapor into ice crystals. This typically occurs in the upper atmosphere, where temperatures are significantly colder than at ground level. However, snow can also form at ground level if the temperature is at or below freezing.

Moisture is the other crucial component required for snow formation. This moisture can originate from various sources, including bodies of water such as lakes and oceans, or from moist air masses. When this moisture-laden air rises, it cools, and the water vapor condenses to form ice crystals. These ice crystals then cluster together to create snowflakes.

The size and shape of snowflakes can vary based on temperature and humidity conditions. For instance, in extremely cold environments, snowflakes tend to be small and powdery, whereas in warmer conditions, they may appear larger and more wet. The process of snow formation is complex, requiring a delicate balance of temperature and moisture conditions to develop effectively.