A snowball is a spherical

Sphere

A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 object made from snow

Snow

Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

, usually created by scooping snow with the hands, and compacting it into a roughly fist-sized ball. The snowball is often used to engage in games, such as snowball fight

Snowball fight

A snowball fight is a physical game in which balls of snow are thrown with the intention of hitting somebody else. The game is similar to dodgeball in its major factors, though typically less organized. This activity is primarily played during months when there is sufficient snowfall.Today, the...

s. Snowball fights are usually light-hearted and involve throwing snowballs at one's friends or family. The pressure exerted by the hands on the snow is a determinant for the final result. Reduced pressure leads to a light and soft snowball. Compacting humid or "packy" snow, by applying a high pressure produces a harder snowball or iceball, which eventually can be considered harmful during a snowball fight.

A snowball may also be a large ball of snow formed by rolling a smaller snowball on a snow-covered surface. The smaller snowball grows by picking up additional snow as it rolls. The terms "snowball effect

Snowball effect

Snowball effect is a figurative term for a process that starts from an initial state of small significance and builds upon itself, becoming larger , and perhaps potentially dangerous or disastrous , though it might be beneficial instead...

", "snowballing" and "Y Gasseg Eira

Nantgarw tradition

Nantgarw tradition is a style of Morris dancing from the South and Valleys regions of Wales, specifically the small village of Nantgarw. The style encompasses both handkerchief and stick dances. The dances call for eight dancers in four pairs...

" are named after this process. This technique is often used to create snowmen

Snowman

A snowman is an anthropomorphic snow sculpture. They are customarily built by children as part of a family project in celebration of winter. In some cases, participants in winter festivals will build large numbers of snowmen...

.

There are some temperature/humidity ranges that prohibit or restrict the formulation of a snowball. With a powdery snow, snowballs are difficult to form. In temperatures below 0 °C (32 °F), there is little free water in the snow, which leads to crumbly snowballs. At 0 °C (32 °F) or above, melted water in the snow results in a better cohesion. If you're walking on snow and it squeaks, chances are the temperature/humidity level won't form a snowball, because squeaking means that the snow is dry.

Self rolling snowballs

Under certain, rarely occurring circumstances, self rolling snowball

Snow roller

A snow roller is a rare meteorological phenomenon in which large snowballs are formed naturally as chunks of snow are blown along the ground by wind, picking up material along the way, in much the same way that the large snowballs used in snowmen are made....

s form on their own.
These circumstances are:

• The ground must have a top layer of ice. This will prevent the snowball from sticking to the ground.
• That ice has to have some wet and loose snow that is near its melting point.
• The wind has to be strong enough to push them. Yet, it cannot be too strong.
• Also, gravity could cause the snowballs to form instead of the wind.

Because these conditions have to take place at the right place in the right time, it is considered a phenomenon.