Weather: the present state of the atmosphere and the current conditions Factors that effect the weather: air pressure, wind, temperature, and humidity.

Humidity - the amount of water vapor in the air. solar energy evaporates water creating water vapor in the atmosphere more vapor is present at warm temperatures than at cold temperatures this is because the space between molecules expands as the air warms up, but is smaller as it cools

Relative Humidity - the amount of water vapor in the air compared to the amount it could hold at a specific temperature -weather forecasters share humidity as this -ex: if it is 50% humidity, that means the air is holding 50% of water vapor it could hold at that temperature

Saturated- Dew Point when the air holds as much water vapor as possible, or 100% humidity. the temperature at which water vapor in the air will condense and turn back to liquid.

- form from warm moist air rising in the atmosphere -as they rise the water vapor cools and condenses into tiny water drops -these drops form around small particles of dust, salt, and smoke in the atmosphere -when millions of these drops collect together, a cloud is formed

Cloud Types- classified by shape and altitude stratus -form layers or smooth sheets in the sky -usually at low altitudes -usually fair (good) weather or precipitation (rain) -can form near the ground called FOG

cumulus -puffy white clouds with flat bottoms -form when air currents rise up -can rise to high altitudes -usually fair weather or thunderstorms

-cirrus high, thin, white, feathery clouds -high altitudes -contain ice crystals -indicate fair weather, but may indicate approaching storms

nimbus -dark clouds -associated with precipitation -dark because they are so full of water vapor, no light penetrates

cumulonimbus towering thunder clouds -caused by warm and cold fronts colliding -precipitation is heavy rains and hail

Precipitation Rain- formed by saturated air that condenses to form rain Sleet- formed by snow passing through warm air and melts, then refreezes near the ground Snow- formed when water vapor condenses in very cold air and changes directly to a solid Hail-formed in thunderstorms when drops of water continue to freeze in layers around a small nucleus of ice