Cities tend to struggle with heavy rain. Without soil to soak up excess water, drains can overflow and roads turn into streams. Daily life is brought to a standstill.
Some cities, of course, have more practice than others – but identifying the world’s rainiest city is not straightforward.
A map of World Bank data shows that the rainiest countries in the world are clearly centred around the equator – the top of South America, in central and west Africa, and among the islands of south-east Asia – but the World Bank doesn’t specify city-level data.
It is, though, possible to look up locations in those areas individually to find online data collected from local weather stations.
The highest recorded rainfalls are in remote places where few people live. Looking at Asia first, two small towns in north-east India – Mawsynram and nearby Cherrapunji – vie for the title of “wettest place on Earth”. The average annual rainfall in Mawsynram, which is recognised as the world’s wettest by the Guinness Book of Records, is 11,871mm – more than 10 times the Indian national average of 1,083mm.
If we limit our focus to large cities, the Indian megacity of Mumbai (2,386mm average annual rainfall) and the city state of Singapore (2,378mm) could feasibly lay claim to the top spot. The capital of the Philippines, Manila, receives 2,047mm annually and the Indonesian capital of Jakarta gets 1,855mm.
In Africa, annual precipitation in Liberia’s capital, Monrovia, can exceed 5,000mm, according to the Liberian Hydrological Services. It is known as the “wettest capital city” by residents and its dampness is no doubt due to its location on a peninsula jutting into the Atlantic Ocean. The port city, home to just over a million people, gets an average of 996mm in July alone. The rainy season can cause havoc, as potholes fill with water and roads turn to rivers.
Hilo, Hawaii’s largest city, is often cited as the rainiest city in the US, with 3,459mm a year. The mountains of the state’s Big Island neatly divide its rainy north from its dry south-west, with one side exposed to wet weather and the other protected. Hilo is in the north-east.
In South America, Colombia has a few claims to rainiest city. The remote city of Quibdó is sometimes cited as the rainiest in the world, with average rainfall of 7,328mm a year, according to one estimate from local weather station data. Home to 125,000 people, the city is a former slave-trading hub that sits on the banks of the Atrato River and is surrounded by dense tropical rainforest. Despite being just 40 miles from the Pacific Ocean, Quibdó can only be reached from the coast by air.
It is not unusual in Quibdó for rain to fall every day in some months, yet it has no reliable source of drinking water. “In Quibdó people live from rainwater,” says the academic Edwar Calderón, who spent three years studying in the city. “About 85% of the population drink water collected in containers on their rooftops. People with money can afford to buy bottles of water, but most of the population is poor so they collect and then boil the rainwater. It is an essential part of life.”
But while vital for survival, rainfall paralyses the city. “It will rain very heavily for four or five hours at a time,” Calderón says. “People get stuck under shelter where they are for the whole of that time.”
Two smaller places in Colombia – López de Micay and Lloró – have also competed for the title of rainiest inhabited place on Earth. López de Micay had an estimated average annual rainfall between 1960 and 2012 of 12,892.4 mm – which would rank it above even Mawsynram in India – but the statistics provided by the Colombian meteorological service have been disputed due to gaps in the record. Similarly, Lloró recorded an average annual rainfall rate of 12,717mm between 1952 and 1989. With populations of 20,000 and 11,000 respectively, neither match Quibdó for city status.
In places such as Britain and the northern US, cities typically suffer from high numbers of drizzly, overcast days rather than heavy bursts of rain. For the likes of Manchester and Seattle, a reputation for rain is a well-known part of their charm, even when the data does not always back that reputation up.
A Met Office analysis from 2014 found that Cardiff was in fact the UK’s rainiest city with an average 1,152mm of rain every year, followed closely by Glasgow. Manchester, with 867mm, only came eighth.
Similarly, Seattle is not the rainiest mainland American city, says Brian Brettschneider, a climate scientist based in Alaska who creates maps for his blog based on climate data in the US.
“When I made the map about the rainiest places in the US, I found that Seattle averages 950mm of precipitation annually, and that is very close to the average value for the entire US,” he says. “Around 45% of the US is wetter than Seattle, counting both rain and melted snow.
“When I published the map on Twitter, a lot of people in Seattle were very upset about it. They take a lot of pride in it being rainy. But somewhere south, like Texas, gets more. It’s just that it falls in about a third of the days that Seattle has rain – whereas there it’s overcast and frequently drizzly.”
To counter the disappointing finding about Seattle, Brettschneider performed a new analysis of places that have what he terms the “dreariest weather”, a measure that combines precipitation (including snow), wet days and cloud cover. East coast and Pacific north-west cities came top on the dreary scale.
“Seattle came very high on that list,” he says. “It is one of the dreariest cities in the US.”
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