How do we know?
↻ One of the pages with a moving picture
Volunteers all over the country measure the rain.
- The Sun warms seas, lakes and rivers. Some water evaporates: it turns into an invisible gas called water vapor and rises.
- High up, the air is cooler. The vapor turns back into tiny droplets, and they make a cloud.
- Droplets bump and join. It takes millions of cloud droplets to make one raindrop!
- When drops get too heavy, they fall as rain. Rivers carry it back to the sea.
Since 1890, volunteers have helped the U.S. weather service. Today more than 8,700 of them take weather readings on farms, in towns and in parks.
Small raindrops are round. Big ones flatten, like a hamburger bun. And some rain dries up before it reaches the ground, in wispy streaks called virga.
Rain can be wild. 1,042 inches of rain fell at Cherrapunji, India, in 12 months (1860–1861). Arica, Chile, once had a dry spell of 172 months, over 14 years!
Wow number
10% of the water vapor in the air comes from plants. They give off water from their leaves.
Myth or fact?
Raindrops are shaped like tears. Myth. Small drops are round. Big ones flatten, like a hamburger bun.
Some rain dries up before it reaches the ground. Fact. These wispy streaks are called virga.
Think about it
The water in your glass may once have been rain. Where could it have been before that?
Where in the world?
Cherrapunji, India where 1,042 inches of rain fell in 12 months (1860–1861). Arica, Chile, once had a dry spell of 172 months — 25.27° N, 91.72° E.
Where these facts come from
Every number on page 32, and who measured it
This page explains how cloud droplets join into raindrops, and what shape raindrops really are.
Precipitation and the Water Cycle — The U.S. Geological Survey, the government's Earth scientists
usgs.gov/special-topics/water-science-school/science/precipitation-and-water-cycle
We checked it on 31 October 2026
This page tells us how much of the water in the air comes from plants.
The Atmosphere and the Water Cycle — The U.S. Geological Survey, the government's Earth scientists
usgs.gov/special-topics/water-science-school/science/atmosphere-and-water-cycle
We checked it on 31 October 2026
This page lists world rain records, like Cherrapunji's 12 months of rain.
HDSC World Record Point Precipitation Measurements — The U.S. National Weather Service
weather.gov/owp/hdsc_world_record
We checked it on 31 October 2026
This official world-records table lists Cherrapunji's rain and Arica's 172-month dry spell.
The World Meteorological Organization, the United Nations' weather agency, which keeps the official world weather records
wmo.int/sites/default/files/2025-07/Table_Records_25Jul2025.pdf
We checked it on 31 October 2026
This page tells us about the volunteer weather watchers who started in 1890.
Cooperative Observer Program (COOP) — The U.S. National Weather Service
weather.gov/coop/overview
We checked it on 31 October 2026
This page tells us what virga is.
NOAA's National Weather Service - Glossary — The U.S. National Weather Service
forecast.weather.gov/glossary.php?word=VIRGA
We checked it on 31 October 2026
Has this changed?
How rain forms is not going to change.
The weather records on this page are records so far. A new wettest or driest spell could beat them.
Words from this page
- evaporate
- To turn from a liquid into an invisible gas.
- water vapor
- Water as an invisible gas in the air.
- virga
- Wispy streaks of rain that dry up before they reach the ground.
Try it!
Make rain in a jar.
1. Ask a grown-up to fill a glass jar one-third full of warm tap water. 2. Put a small plate on top. Pile ice cubes on the plate. 3. Wait 5 minutes. Look at the bottom of the plate.
What happens: drops form under the cold plate, join up and drip down, like rain from a cloud.
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