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Clouds and Weather Study Guide
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Weather scientists classify a cloud based on its shape, its color, and where it
forms in the atmosphere. The clouds you see are likely to be all the same type.
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Because clouds form along a front, they can help predict weather.
Clouds
1. Cirrus – wispy, high-altitude clouds that are made up of ice crystals. Wind
stretches them into long, wispy horsetail or feather shapes. They usually go
with cooler, fair weather.
2. Cumulonimubus – towering, dark rain clouds with a nimbus, or halo, of
gray-white. If a cold front moves past, you’ll probably see these clouds. If
you see them, it’s probably going to rain soon.
3. Cumulus – puffy, cotton-ball clouds that begin to form when water droplets
condense at middle altitudes. Look for them on clear, warm days. They can
become cumulonimubus, or thunderstorm, clouds.
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4. Stratus – flat layer of low clouds. Light rain, drizzle, or flurries likely,
overcast skies at best. You see these clouds on a gray, cloudy day. Stratus
clouds form a low layer of dark gray. They can occur along warm fronts.
Sometimes they bring light rain or snow showers.
Air Masses Move
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You can see air masses moving from place to place by watching how weather
forms and changes.
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Wind speed often increases as a front approaches. Wind direction also changes.
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Air pressure also changes as air masses move over an area.
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As a cold front moves closer, air pressure often drops.
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Air pressure usually rises as the cold front moves over the area.
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Temperature, too, changes as a front moves over an area.
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Warmer air is brought into a region by a warm front.
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The temperature goes down when a cold front moves through an area.

Air pressure drops as the front moves closer. Air pressure rises as the front moves
over the area.
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Air masses form over continents and oceans.
(Harcourt Science D15-17)