air mass

American  

noun

1. a body of air covering a relatively wide area, exhibiting approximately uniform properties through any horizontal section.

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air mass British  

noun

1. a large body of air having characteristics of temperature, moisture, and pressure that are approximately uniform horizontally

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air mass Scientific  

1. A widespread body of air that originates over a large area of land or ocean and assumes the temperature and humidity of that area, with characteristics distributed fairly evenly throughout the horizontal layers of the mass. Air that stands over the Caribbean Sea, for example, becomes a warm, humid maritime tropical air mass, while air that lies in the Arctic regions of northern Canada takes on the cold and dry characteristics of its surroundings and becomes a continental polar air mass. When air masses of differing properties come into contact in the middle latitudes, they frequently generate storm fronts.

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Etymology

Origin of air mass

First recorded in 1890–95

Example Sentences

"This finally breaks, allowing a northerly air mass to set in, bringing much drier, brighter conditions, sunshine on the way on Friday and Saturday and a few wintry showers on Friday."

From BBC • Feb. 12, 2026

Strong high pressure over eastern Europe and Scandinavia has locked in a very cold air mass, while an active jet stream has steered a succession of Atlantic low-pressure systems towards the UK.

From BBC • Jan. 28, 2026

The storm was expected to linger for days, shifting into the heavily populated mid-Atlantic and northeastern states while crippling daily life and ushering in a frigid air mass across the country.

From Barron's • Jan. 23, 2026

But even when rain isn’t falling, Southern California will feel the effects of the moist air mass over the region.

From Los Angeles Times • Sep. 18, 2025

Hubbard began to explain that a tropical air mass was moving in from— Groves cut Hubbard off.

From "Bomb" by Steve Sheinkin