Section 2: Weather
The atmosphere is the air that surrounds the earth. Weather refers to the condition of the atmosphere concerning temperature, wind, amount of cloudiness, precipitation, and humidity. Weather is the day-by-day condition of the atmosphere.
Precipitation is any kind of moisture that falls from the atmosphere. It may be liquid or solid. Rain, drizzle, sleet, snow, and hail are forms of precipitation. Rain falls as liquid water. The amount of rain coming down from the clouds can vary from a misty drizzle with very small drops to a heavy downpour. Sleet is rain that freezes into pellets before it reaches the ground; and hail is small, round pieces of ice. Snow is water that is frozen into crystals and falls to the earth in soft, white flakes.
Dew, frost, and fog are not forms of precipitation because they do not fall from the atmosphere. Dew is moisture that condenses from the air and gathers in small drops on cool surfaces. Dew is what makes the grass wet in the mornings during the summer. It can be compared with the moisture that appears on the outside of a glass of ice water. If the temperature is below freezing, the moisture forms frost.
When warm air containing a lot of moisture moves over cold ground, the cold surface cools the air, and fog is formed. Fog is actually a cloud that is on the ground.
Humidity is the amount of moisture in the air. The amount of moisture that air can hold depends on the temperature. Warm air can hold more moisture than cold air. When the humidity is high, a hot day feels much hotter, and a cold day feels much colder than it does when the humidity is low. The Red River Valley is more humid than the rest of the state, so summer days may feel warmer and winter days may feel colder than in other parts of the state. Overall, however, the humidity in North Dakota is fairly low compared with many other places.
Weather is reported by meteorologists. Meteorologists also make weather forecasts, predicting what the weather will be like in the days to come. They use many scientific tools to help them forecast the weather, including satellites from outer space that take photos of weather happenings on the earth.