Clouds get their shapes by the air that surrounds them. We have all experienced those days when the clouds seem like a blanket covering the sky. Just a solid grey, flat cloud hovering in the sky. These are referred to as stratus clouds. Stratus clouds come from the Latin word “stratus” which means layer.

These clouds are formed under stable conditions and can sometimes stay in the same location for days at a time. They form when warm, moist air cools down and reaches dew point (which is the temperature at which the air becomes saturated with moisture). This cooling occurs from various factors, such as:

• Radiational cooling - This occurs overnight when the Earth’s surface loses heat, therefore cooling the air close to the ground.
• Frontal lifting - When a warm air mass meets a cold air mass (such as a warm front or cold front). The warm air is forced to rise, cool, and condense into stratus clouds.
• Orographic lifting - When moist air is forced to ascend over a mountain range, it cools as it rises and if the conditions are just right, stratus clouds may form.

In California, a "marine layer" can form, which is a layer of cool, moist air that develops over a large body of water, like an ocean, when warm air moves over a colder water surface, often causing fog or low-lying clouds to form due to the temperature inversion created; it's particularly prevalent along coastlines and is often associated with terms like "May Gray" or "June Gloom" in California.

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Because stratus clouds form at such a low altitude (typically below 2,000 ft, but can form as high as 4,000 ft), the droplets within the clouds remain in liquid form.

This segment originally appeared in today's edition of the Morning Brief newsletter. Sign up here to get weekday updates from The Weather Channel and our meteorologists.

J​ennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.