Rain

Hard rain on a roof
Rain falling on a field, in southern Estonia
Streets in Tampere, Finland watered by night rain.
The shape of rain drops depending upon their size
Black Rain Clouds
A raindrop on a leaf
Convective precipitation
Orographic precipitation
Rainfall distribution by month in Cairns showing the extent of the wet season at that location
Image of Atlanta, US showing temperature distribution, with blue showing cool temperatures, red warm, and hot areas appearing white.
Average surface air temperatures from 2011 to 2020 compared to the 1951–1980 average. Source: NASA
Band of thunderstorms seen on a weather radar display
Sources of acid rain
Updated Köppen–Geiger climate map
Standard rain gauge
Twenty-four-hour rainfall accumulation on the Val d'Irène radar in Eastern Canada. Zones without data in the east and southwest are caused by beam blocking from mountains. (Source: Environment Canada)
Example of a five-day rainfall forecast from the Hydrometeorological Prediction Center
Rainfall estimates for southern Japan and the surrounding region from July 20–27, 2009.
A rain dance being performed in Harar, Ethiopia
Rain, depicted in the 1493 Nuremberg Chronicle
Largest deserts
Isolated towering vertical desert shower
Long-term mean precipitation by month

Liquid water in the form of droplets that have condensed from atmospheric water vapor and then become heavy enough to fall under gravity.

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Wet season

The rainfall distribution by month in Cairns, Australia.
A wet season storm at night in Darwin, Australia.
A monsoon in the Vindhya mountain range, central India.
Equatorial savanna in the East Province of Cameroon.

The wet season (sometimes called the rainy season) is the time of year when most of a region's average annual rainfall occurs.

Irrigation

Agricultural process of applying controlled amounts of water to land to assist in the production of crops, as well as to grow landscape plants and lawns, where it may be known as watering.

Irrigation of agricultural fields in Andalusia, Spain. Irrigation canal on the left.
Animal-powered irrigation, Upper Egypt, ca. 1846
Young engineers restoring and developing the old Mughal irrigation system in 1847 during the reign of the Mughal Emperor Bahadur Shah II in Indian subcontinent
Inside a karez tunnel at Turpan, Xinjiang, China
Share of agricultural land which is irrigated (2015)
Basin flood irrigation of wheat
Residential flood irrigation in Phoenix, Arizona, US
Drip irrigation – a dripper in action
Drip irrigation layout and its parts
Crop sprinklers near Rio Vista, California, US
A traveling sprinkler at Millets Farm Centre, Oxfordshire, United Kingdom
A small center pivot system from beginning to end
Rotator style pivot applicator sprinkler
Center pivot with drop sprinklers
Wheel line irrigation system in Idaho, US, 2001
Center pivot irrigation
An impact sprinkler watering a lawn, an example of a hose-end sprinkler
Irrigation is underway by pump-enabled extraction directly from the Gumti, seen in the background, in Comilla, Bangladesh.
Grapes in Petrolina, Brazil only made possible in this semi arid area by drip irrigation
Overirrigation because of poor distribution uniformity in the furrows. Potato plants were oppressed and turned yellow
upright|thumb|The hub of a center-pivot irrigation system
thumb|Leaks in micro-irrigation drip lines
thumb|Sprinkler irrigation of blueberries in Plainville, New York, United States
thumb|Irrigation in Tamil Nadu, India
thumb|upright|Irrigation ditch in Montour County, Pennsylvania, USA
thumb|Water gardens in Sigiriya, Sri Lanka
thumb|Micro-sprinkler

Archaeological investigation has found evidence of irrigation in areas lacking sufficient natural rainfall to support crops for rainfed agriculture.

Fresh water

Any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids.

Visualisation of the distribution (by volume) of water on Earth. Each tiny cube (such as the one representing biological water) corresponds to approximately 1400 cubic km of water, with a mass of approximately 1.4 trillion tonnes (235000 times that of the Great Pyramid of Giza or 8 times that of Lake Kariba, arguably the heaviest man-made object). The entire block comprises 1 million tiny cubes.
A graphical distribution of the locations of water on Earth. Only 3% of the Earth's water is fresh water. Most of it is in icecaps and glaciers (69%) and groundwater (30%), while all lakes, rivers and swamps combined only account for a small fraction (0.3%) of the Earth's total freshwater reserves.

Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes.

Rainband

Cloud and precipitation structure associated with an area of rainfall which is significantly elongated.

Band of thunderstorms seen on a weather radar display
A February 24, 2007 radar image of a large extratropical cyclonic storm system at its peak over the central United States. Note the band of thunderstorms along its trailing cold front.
Photograph of rainbands in Hurricane Isidore

Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of rain or snow.

Drop (liquid)

Small column of liquid, bounded completely or almost completely by free surfaces.

Water drops on a leaf
Water drops falling from a tap.
Rain water flux from a canopy. Among the forces that govern drop formation: surface tension, cohesion, Van der Waals force, Plateau–Rayleigh instability.
Raindrops in a plant.
Drop of water bouncing on a water surface subject to vibrations
The pendant drop test illustrated.
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The capillary length L_c against radii of a droplet
Blue dye being dropped in a saucer of milk.
Impact of a drop of water.
Backjet from drop impact.
A drop of water hitting a metal surface/ crown formation due to splashing of droplet.
A drop of water hitting a wet metal surface and ejecting more droplets, which become water globules and skim across the surface of the water.
A drop of water on a leaf / Hydrophobic effect/ Partial Wetting.
A triple backjet after impact.
Photo of a raindrop on a fern frond.
Detaching drop.
Water droplets forming out of a shower head.
A drop of water on an Asteraceae
Droplets of water refracting a small flower.
A raindrop on a leaf
Water droplets on glass.
Fountain water droplets as seen in very short exposure
Rain droplets on Rose plant leaf

Due to the different refractive index of water and air, refraction and reflection occur on the surfaces of raindrops, leading to rainbow formation.

Water cycle

Biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth.

Time-mean precipitation and evaporation as a function of latitude as simulated by an aqua-planet version of an atmospheric GCM (GFDL's AM2.1) with a homogeneous “slab-ocean” lower boundary (saturated surface with small heat capacity), forced by annual mean insolation.
Global map of annual mean evaporation minus precipitation by latitude-longitude
Relationship between impervious surfaces and surface runoff
Diagram of the water cycle
Natural water cycle

Precipitation: Condensed water vapor that falls to the Earth's surface. Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet. Approximately 505000 km3 of water falls as precipitation each year, 398000 km3 of it over the oceans. The rain on land contains 107000 km3 of water per year and a snowing only 1000 km3. 78% of global precipitation occurs over the ocean.

Cumulonimbus cloud

Dense, towering vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents.

Cumulonimbus calvus cloud in Monterrey, Mexico.
Partial view of a cumulonimbus cloud, possibly an arcus cloud.
Pyrocumulonimbus with pileus
Stages of a cumulonimbus cloud's life.
Transformation from a mature cumulus congestus cloud to a mature cumulonimbus incus
Cumulonimbus calvus
A clearly developed cumulonimbus fibrous-edged top capillatus
A freeze-frame of a Cumulonimbus cloud in the distance exposing a flash of lightning
Arcus cloud (shelf cloud) leading a thunderstorm
A cap (pileus) atop a congestus
Incus with a velum edge
Mammatocumulus with drooping pouches
A funnel cloud (tuba) over the Netherlands
Flanking line in front of a strong thunderstorm
An overshooting top is a dome of clouds atop a cumulonimbus
Cumulonimbus calvus against sunlight with rain falling beneath it as a rain shaft.
Rain evaporating before reaching the ground (virga)

Rain: precipitation that reaches the ground as liquid, often in a precipitation shaft.

Precipitation

Any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds.

Mean precipitation based on global high resolution climate data (CHELSA)
Countries by average annual precipitation
A thunderstorm with heavy precipitation
Late-summer rainstorm in Denmark
Lenticular cloud forming due to mountains over Wyoming
Condensation and coalescence are important parts of the water cycle.
Puddle in the rain
An accumulation of ice pellets
A large hailstone, about 6 cm in diameter
Snowflake viewed in an optical microscope
Convective precipitation
Orographic precipitation
Lake-effect snow bands near the Korean Peninsula in early December 2008
Rainfall distribution by month in Cairns showing the extent of the wet season at that location
Standard rain gauge
Updated Köppen-Geiger climate map
Rainfall estimates for southern Japan and the surrounding region from July 20 to 27, 2009.
Extreme precipitation events have become more common in the U.S. over recent decades.
Image of Atlanta, Georgia, showing temperature distribution, with hot areas appearing white
Example of a five-day rainfall forecast from the Hydrometeorological Prediction Center

The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail.

Extratropical cyclone

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth.

A powerful extratropical cyclone over the North Atlantic Ocean in March 2022
Approximate areas of extratropical cyclone formation worldwide
An upper-level jet streak. DIV areas are regions of divergence aloft, which will lead to surface convergence and aid cyclogenesis.
Hurricane Cristobal (2014) in the north Atlantic after completing its transition to an extratropical cyclone from a hurricane
QuikSCAT image of typical extratropical cyclones over the ocean. Note the maximum winds are on the outside of the occlusion.
Extratropical cyclones spin clockwise in the Southern Hemisphere, just like tropical cyclones.
A hurricane-force extratropical cyclone in January 2016 with a distinct eye-like feature, caused by a warm seclusion
A zonal flow regime. Note the dominant west-to-east flow as shown in the 500 hPa height pattern.
A February 24, 2007 radar image of a large extratropical cyclonic storm system at its peak over the central United States.
Preferred region of snowfall in an extratropical cyclone
Cyclone Oratia showing the comma shape typical of extratropical cyclones, over Europe in October 2000.

Extratropical cyclones are capable of producing anything from cloudiness and mild showers to severe gales, thunderstorms, blizzards, and tornadoes.

Rain shadow

Effect of a rain shadow
The Tibetan Plateau (center), perhaps the best example of a rain shadow. Rainfalls from the southern South Asian monsoon do not make it far past the Himalayas (seen by the snow line at the bottom), leading to an arid climate on the leeward (north) side of the mountain range and the desertification of the Tarim Basin (top).
The Atlas mountains' (top) rain shadow effect makes the Sahara even drier.
The mountain ranges on the eastern side of Madagascar provide a rain shadow for the country's western portion.
The eastern regions of the Western Ghats lie in a rain shadow, receiving far less rainfall.
Most of Iran is rain-shadowed by the Alborz mountains in the north (just south of the Caspian sea), hence the country's mostly (semi) arid climate.
Lake Urmia (centre) and surrounds rain-shadowed by the snowy Zagros mountains to the west.
Cantabrian Mountains in the north, which rain-shadow most of Spain.
The Cascade Range to the North, the California Coast Ranges to the West and the Sierra Nevada Mountains to the East provide a significant rain-shadow for the inland North American deserts.
The Atherton Tableland rain-shadowing the dry Tablelands Region in Queensland (bottom-right).
The Southern Alps in New Zealand rain shadow the eastern side of the South Island.
The Andes mountains block rain and moisture from the Amazon basin to the west (Bolivia).

A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side.