Air masses: Regions and classifications

KOIN 6 Weather Kids
oregon coast
Weekend Meteorologist Joseph Dames

PORTLAND, Ore. (KOIN) – Let’s talk about air masses!

Wait, wait, wait: what exactly is an air mass? Think about a large body of air with similar temperature and moisture.

These air masses typically originate in specific locations in North America and will represent the type of characteristics that part of the country handles. To be specific, these are the air mass classifications for the United States with a bonus classification that will mostly impact those much further north in Canada.

This is one of my favorite topics because it is quick and specific. You just have to know a few terms and you can breakdown the general climate for each part of the United States, based on the air mass that impacts that region.


Generic Air Mass Classification

The best way to think about this is to break everything into categories and then combine them appropriately.

We can start with two general categories, moisture and temperature.

There are two classifications for moisture: Marine (moist) and Continental (dry).

We also work with three types of temperature classifications: Tropical (warm), Polar (cold) and Arctic (very cold).

That isn’t too many categories to have to comprehend and they all make sense when you think about each location and if they’re close to water or more of a landlocked location. Now what makes this a little more fun, is that you combine the two categories to give each location an air mass classification. You do this with using a lower case moisture category with an upper case temperature classification.

For example – mP is the air mass that we typically experience in the Pacific Northwest. It makes sense because we are near the ocean (marine) and we are situated right in the mid-latitudes away from the tropics. That means we take the small “m” that represents marine and combine it with the upper case “P” that represents polar.


Miami, Florida:

Austin, Texas:

Minneapolis, Minnesota:

Phoenix, Arizona:

Denver, Colorado:

New York City, New York:

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