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b. Warm air usually has higher humidity. As the warm air is lifted, its temperature is

lowered. As the lifting process continues, the moisture in the air condenses. Low

nimbostratus and stratus clouds form, and Any drizzle and rain develop. The rain falls

through the colder air below, increasing its moisture content so that it also becomes

saturated. Any reduction of temperature in the colder air may result in extensive fog. The

temperature of the cold air may be reduced when the ground cools after the sun goes down,
or it may be reduced by the colder air moving up and rising over sloping terrain such as hills

or mountains. As stable warm air moves up the slope of the front and the temperature of

the warm air continues to fall, clouds appear at increasingly higher levels in the form of

altostratus (middle height) and cirrostratus (high altitude) clouds.