Honestly, if you’ve ever been caught in a summer downpour without an umbrella, you know how fast a street can turn into a river. It’s a mess. But the kind of rain we’re talking about here—the actual, verified world record for the most rain in 24 hours—is basically a different physical reality. We aren't talking about a "heavy storm." We are talking about the sky literally falling.
The official number is 1,825 mm (71.8 inches).
That happened on January 7–8, 1966, at a place called Foc-Foc on Reunion Island. To put that in perspective, that is nearly six feet of water falling from the clouds in a single day. If you stood outside in it, the water would be over the head of the average person by the time the clock hit the 24-hour mark.
Why Reunion Island keeps winning the rain game
You might be wondering where the heck Reunion Island even is. It’s a tiny French territory in the Indian Ocean, sitting east of Madagascar. It is beautiful, volcanic, and apparently, a massive magnet for tropical cyclones.
The 1966 record was fueled by Tropical Cyclone Denise.
When these massive storms hit the island’s steep, jagged mountains (we’re talking peaks nearly 10,000 feet high), the air is forced upward so fast it cools and dumps every drop of moisture it’s holding. Meteorologists call this orographic lift. Basically, the mountains act like a giant squeegee for the clouds.
The "Old Mistake" at Cilaos
For years, people cited a different record: 1,870 mm at Cilaos in 1952. You'll still see this in some old textbooks or random blogs. However, the World Meteorological Organization (WMO) eventually flagged this as a measurement error. It was "an old mistake," according to the pros at Météo-France. So, Foc-Foc holds the crown.
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Reunion doesn't just hold the 24-hour record, either. It pretty much owns the leaderboard for anything from 12 hours up to 15 days. During Cyclone Hyacinthe in 1980, one spot on the island recorded over 6,000 mm of rain in two weeks. That’s just... unsustainable for a normal life.
Cherrapunji and Mawsynram: The monsoon heavyweights
While Reunion Island takes the prize for the single most intense 24-hour "burst," you can't talk about rain without mentioning Meghalaya, India.
The villages of Mawsynram and Cherrapunji are famous. They don't just get hit by one-off cyclones; they get the monsoon. Every year. Like clockwork.
- Mawsynram is widely considered the wettest place on Earth based on annual averages.
- In June 2022, Mawsynram saw a staggering 1003.6 mm in 24 hours.
- Cherrapunji (now often called Sohra) held the 48-hour record for a long time.
It’s a different kind of wet. In these places, the rain is a constant presence for months. People wear "knups"—these giant umbrella-like shields made of bamboo and reeds—just to walk to the market. They build bridges out of living tree roots because regular wood just rots away in the humidity.
What about the United States?
The U.S. records are impressive, but they don't quite touch the tropical madness of the Indian Ocean. For a long time, the record sat in Alvin, Texas, where 42 inches fell during Tropical Storm Claudette in 1979.
Then came Hawaii.
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In April 2018, a "Kona low" storm parked itself over Waipā Garden, Kauai. In 24 hours, it dropped 49.69 inches (1,262 mm). It smashed the Texas record and reminded everyone that Kauai’s Mt. Waialeale isn't called one of the wettest spots in the country for nothing.
A quick look at the US "Wettest" leaderboard:
- Waipā Garden, HI (2018): 49.69 inches
- Alvin, TX (1979): 42.00 inches
- Dierks, AR (2019): 16.17 inches (showing how big the gap is between the islands and the mainland)
How do we actually know these numbers are real?
Measuring the most rain in 24 hours isn't as simple as sticking a bucket in the backyard.
Most of these records come from tipping-bucket rain gauges or weighing gauges. In a tipping bucket, a tiny seesaw mechanism tips every time it collects 0.1 mm or 0.2 mm of rain. An electronic sensor counts the tips. But in a record-breaking storm, the rain can fall so fast the bucket can't tip quickly enough. It just overflows.
That’s why the WMO has a specialized team to verify these things. They look at:
- Gauge calibration: Was the instrument actually working right?
- Siting: Was the gauge too close to a building that might have funneled extra water into it?
- Comparison: Did nearby stations show similar (if slightly lower) numbers?
If the data looks "too clean" or wildly inconsistent with the local geography, they'll toss it. It's a rigorous process because these numbers help engineers design dams and drainage systems that won't fail when the next "Big One" hits.
Why this matters more than just "cool facts"
We live in a world where the atmosphere is getting warmer. Basic physics—the Clausius-Clapeyron relation—tells us that for every degree Celsius of warming, the air can hold about 7% more water vapor.
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That’s a lot of extra fuel.
We’re seeing "thousand-year" rain events happening every few years now. Whether it's the 2024 floods in North Carolina from Hurricane Helene or the massive deluges in Dubai, the intensity is cranking up. Understanding the absolute limits of what the sky can dump—that 1,825 mm benchmark—helps us understand what we might be facing in the future.
Staying safe when the sky opens up
If you ever find yourself in a situation where the rainfall starts creeping toward these record levels, the rules are pretty simple but life-saving.
- Turn around, don't drown. Most flood deaths happen in cars. It only takes 12 inches of rushing water to sweep a car off the road.
- Watch the soil. In places with steep hills (like Reunion or Appalachia), record rain leads to landslides. If you hear a low rumbling or see trees tilting, move immediately.
- Clear your drains. On a personal level, keeping your gutters and local storm drains clear of leaves can be the difference between a dry basement and a total loss.
The record for the most rain in 24 hours is a testament to the sheer power of the Earth's water cycle. It's beautiful, in a terrifying sort of way. While most of us will never see 71 inches of rain in a day, being aware of how fast weather can turn from "wet" to "historic" is just part of being a prepared human in the 21st century.
To stay ahead of extreme weather, keep a battery-powered weather radio on hand and map out the highest elevation points in your immediate neighborhood before the next major storm warning is issued.