Between 3/8 and 5/8 of the sky is covered by clouds. (source #4)

Side note- A better representation of the fraction 3/8 and 5/8 is by using an example of a pizza to represent each of these. 

When 7/8ths or more of the sky is covered by clouds.  (source #4)

Side note: A better representation of the fraction 7/8 is by using an example of how a pizza has 8 slices and one of the slices is missing.

Fog is water droplets suspended in the air at the Earth's surface. Fog is often hazardous when the visibility is reduced to a ¼ mile or less.(source #4)

20 to 30 mph winds. (source #4)

Precipitation that falls to earth in drops more than 0.5 mm in diameter. (source #4)

Precipitation in the form of ice crystals. It has a hexagonal form and often agglomerated (grouped/bunched together) into snowflakes. It is formed directly from the freezing [deposition] of the water vapor in the air. (source #4)

A National Weather Service convective precipitation descriptor for a 10 percent chance of measurable precipitation (0.01 inch). Isolated is used interchangeably with few. (source #4)

An official sky cover classification for aviation weather observations, when the sky is completely covered by an obscuring phenomenon. This is applied only when obscuring phenomenon aloft are present--that is, not when obscuring phenomenon are surface-based, such as fog. (source #4)

An aggregation in the atmosphere of very fine, widely dispersed, solid or liquid particles, or both, giving the air an opalescent appearance that subdues colors. (source #4)