Weather

Weather is the state of the atmosphere at a given time and place. Most weather takes place in the troposphere, the lowest layer of the atmosphere.

Weather is measured and described in a variety of ways by meteorologists, scientists who study and predict weather. Air temperature and pressure, the amount and type of precipitation, the strength and direction of wind, and the types of clouds are all described in a weather report.

Weather changes each day because the air in our atmosphere is always moving, distributing energy from the Sun. In most places in the world, the types of weather events also vary throughout the year as seasons change.

<a href="/earth/Atmosphere/clouds/kelvin_helmholtz.html">Kelvin-Helmholtz</a> clouds resemble breaking <a href="/earth/Water/ocean_waves.html">waves in the ocean</a>. They are usually the most developed near mountains or large hills. Wind deflected up and over a barrier, like a mountain, continues flowing through the air in a wavelike pattern. Complex <a href="/earth/Water/evaporation.html">evaporation</a> and <a href="/earth/Water/condensation.html">condensation</a> patterns create the capped tops and cloudless troughs of the waves.  This image was taken on February 9, 2003 in the morning in Boulder, Colorado.<p><small><em> Courtesy of Roberta Johnson</em></small></p>Hurricane Alex, a <a href="/earth/Atmosphere/hurricane/saffir_simpson.html">category 3</a> storm at its strongest, traveled north along the east coast of North America in August 2004 causing <a href="/earth/Atmosphere/hurricane/surge.html">flooding</a>, strong <a href="/earth/Water/ocean_waves.html">waves</a>, and rip tides along the coast. <a href="/earth/Atmosphere/hurricane/formation.html">Hurricanes form</a> in the tropics over warm ocean water and die down when they <a href="/earth/Atmosphere/hurricane/movement.html">move</a> over land or out of the tropics. These storms are called hurricanes in the Atlantic and typhoons or tropical cyclones in other areas of the world.<p><small><em> Courtesy of NOAA</em></small></p>A <a href="/earth/Atmosphere/tornado.html">tornado</a> begins in a severe <a href="/earth/Atmosphere/tstorm.html">thunderstorm</a> called a <a href="/earth/Atmosphere/tstorm/severe.html">supercell</a>.</p> The wind coming into the storm starts to swirl and forms a funnel. The air in the funnel spins faster and faster and creates a very <a href="/earth/Atmosphere/low_pressure.html">low pressure</a> area which sucks more   This tornado was photographed in Carteret County, NC on June 7, 2004.<p><small><em>Courtesy of National Weather Service Forecast Office of Newport/Morehead City, NC</em></small></p>This photograph of a <a href="/earth/Atmosphere/clouds/cumulonimbus.html">cumulonimbus cloud</a> was taken on the <a href="/earth/grassland_eco.html">grasslands</a> of eastern Wyoming. Notice the <a href="/earth/Atmosphere/precipitation/rain.html">rain</a> and <a href="/earth/Atmosphere/precipitation/hail.html">hail</a> falling from this cloud! Cumulonimbus clouds form during <a href="/earth/Atmosphere/tstorm.html">thunderstorms</a>, when very warm, moist air rises into cold air. As this humid air rises, water vapor <a href="/earth/Water/condensation.html">condenses</a>, and forms huge <a href="/earth/Atmosphere/clouds/cumulonimbus.html">cumulonimbus</a> clouds. <p><small><em> Photo courtesy of <a href="http://www.inclouds.com">Gregory Thompson</a></em></small></p>

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Explore Weather

Weather Fronts

When a front passes over an area, it means a change in the weather. Many fronts cause weather ...Read more

Clouds

Clouds can come in all sizes and shapes, and can form near the ground or high in the atmosphere. ...Read more

Thunderstorms

Thunderstorms are one of the most thrilling and dangerous types of weather phenomena. Over ...Read more

Tornadoes

Tornadoes form from severe thunderstorms. They have a very high energy density which means ...Read more

Hurricanes

As a strong hurricane heads towards a vulnerable coast, people take precautions - boarding ...Read more

Heat Waves

It’s the middle of the summer and it’s hot – hotter than normal. The heat lasts for days. It’s ...Read more

Blizzards

Fast winds blowing up to 75 mph (120 kph), 43 inches (1 meter) of snowfall, power outages, ...Read more

Urban Weather

Cities can affect the weather. Looking at satellite data, scientists have observed that heavy ...Read more

Atmospheric Optics

Have you ever seen clouds in the sky that looked different than "normal" clouds? Or have you ...Read more

Weather Instruments

Knowing what weather is on the way is important to many people. For example, farmers plan their ...Read more

More about Weather

Did you know?

Did you know that you can now share your poems about our collection of cloud art photos. Have fun!

Did you know that the upper atmosphere of the Earth overlaps with the Earth's ionosphere?

 

Earth and Space Science Concept of the Day

Do you know what this word or phrase means?

Epicenter
xEpicenter : The epicenter is the point on the earth's surface vertically above the hypocenter (or focus), point in the crust where a seismic rupture begins.

Click on the word to find out!

Research Highlights

Triggers of Volcanic Eruptions in Oregon's Mount Hood Investigated

A new study has found that a mixing of two different types of magma is the key to the historic eruptions of Mount Hood, Oregon's tallest mountain, and that eruptions often happen in a relatively short...Read more

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