Meteorologists define the wettest places by two metrics: the highest total volume of water annually, and the highest frequency of rainy days throughout the year. These two measures often point to different regions, demonstrating that a place can receive a staggering amount of rain in a short time or a moderate amount spread over many days. These record-breaking locations reveal the capacity of the atmosphere to generate precipitation when moisture, uplift, and topography align.
The Wettest Places on Earth (By Volume)
The world record for the highest average annual rainfall is held by Mawsynram, a village in the Meghalaya state of India, which receives approximately 467 inches (11,871 millimeters) of rain per year. This measurement is an average taken over many decades, underscoring the consistent nature of the extreme precipitation. The nearby town of Cherrapunji, which historically held the record, remains a close second.
South America hosts locations that rival these Asian records, particularly in the Chocó Department of Colombia, bordering the Pacific Ocean. The region around Lloró and López de Micay claims annual precipitation figures that can exceed 500 inches (12,700 millimeters). These localized areas demonstrate rainfall accumulation comparable to the Indian record holders, representing nearly 39 feet of water falling from the sky each year.
The Science Behind Extreme Rainfall
The phenomenal rainfall in the Khasi Hills of India is driven by a meteorological mechanism called orographic lifting, combined with the summer monsoon. Orographic lifting occurs when moisture-laden air encounters a mountain range and is forced upward along the slope. As the air rises, it expands and cools, causing the water vapor within it to condense rapidly and form clouds.
In the case of Mawsynram and Cherrapunji, the Bay of Bengal branch of the southwest monsoon carries moist air across the plains of Bangladesh. The air channels into the funnel-shaped valley created by the Khasi, Garo, and Jaintia Hills, which are perpendicular to the monsoon flow. This unique topography acts as a barrier, forcing the saturated air to ascend to a high elevation where it cools dramatically, releasing its moisture in a concentrated deluge on the windward side.
Locations Defined by Constant Rain Frequency
While Mawsynram receives the highest volume, other locations are defined by the frequency of rainfall, experiencing rain on a majority of days each year. Cherrapunji averages over 320 rainy days annually, meaning that it rains on more than four out of every five days. This contrasts with high-volume areas where the rain may fall less often but in heavy downpours.
Hilo, on the windward side of the Big Island of Hawaii, averages around 275 rainy days per year. This constant precipitation is a direct result of the persistent Pacific trade winds pushing moist air up the slopes of Mauna Loa and Mauna Kea. Similarly, parts of the Chocó region in Colombia, such as Buenaventura, regularly record over 250 days of measurable rainfall per year. These frequent-rain locations are characterized by a perpetual pattern of light rain or mist, often referred to as perpetual drizzle, keeping the landscape continually saturated.