Rain is in the forecast for this Sunday, so a story about the formation of raindrops seems appropriate. Once you read this story you will be an expert on raindrops, so you might as well keep reading so you can impress all of your friends!

The compound H2O exists on the planet Earth in three phases: water (liquid), ice (solid), water vapor (gas). In fact, H2O is the only substance that is known to exist in all three phases in nature which is one of it’s many unique qualities.

While H2O does precipitate as a solid during the winter (snow, sleet, freezing rain, etc.) by far the most common type of precipitation is rain. The majority of rain falls in rainforest climates near the equator where up to 400 inches of rain can fall each year!

The mechanism of raindrop development is relatively simple. When water vapor in the atmosphere is displaced vertically, the water vapor cools with increasing elevation. Once the gaseous water reaches a certain temperature known as the dewpoint temperature (also called condensation level), the water vapor will condense and form cloud droplets.

If the atmosphere has enough water vapor and there is enough vertical air displacement then the cloud droplets will eventually form into raindrops.

Graphic showing the formation of clouds which eventually form into raindrops.

Raindrops will continue to grow in size during this time. Raindrops can grow by colliding with each other or they can also grow by further condensing water vapor into liquid water. Regardless of the mechanism, eventually the raindrops will fall to the surface of the Earth. During this time, the raindrops can break up, evaporate, or continue their descent. If the air has enough moisture then the raindrops will fall to the surface as rain.

Fascinating rain facts

Largest raindrop ever recorded: The largest raindrops ever recorded were located in the Amazon rainforest of Brazil in 1995. The drops were eight millimeters in diameter which is about 1/4th the size of a golf ball! Most raindrops range in size between one and five millimeters.

Most rain recorded in a day: The most rain ever recorded in a day is 71.8″ (nearly 6 feet)! This heavy rain was recorded in Foc-Foc, La Reunion which is a remote island east of Madagascar in the Indian Ocean.

This measurement was made during the passage of Tropical Cyclone Denise on January 7, 1966. La Reunion is characterized by its mountainous terrain which locally enhances the precipitation over the island. The island is notorious for heavy rainfall amounts and hold several records for the heaviest rainfall recorded for different time intervals.

Most rain recorded in a year: The most rain ever recorded in a year was 1,042 inches in Cherrapunji,India which fell between August 1860 and July 1861!

Although the month has started off with wet conditions, thankfully we will not be seeing rain like those astonishing facts above!