Did You Know?
A City with 98% Humidity and Almost No Rain
1. Lima gets under 10 millimetres of rain a year.
Estimates vary between about 7 and 16 millimetres depending on the measuring period, but the picture is consistent: this is one of the driest capital cities on Earth, alongside Cairo. It is also the world's second-largest desert city, after Cairo.
For comparison, London gets around 600 millimetres. Lima receives roughly one-eightieth of that.
2. And yet the humidity reaches 98%.
The cold Humboldt Current runs up this coast, chilling the air above it. Cold air holds less moisture, so instead of rain the city gets garúa — a persistent grey drizzle-fog that sits over Lima for months at a time.
The result is a genuine climatic oddity: Lima records around 1,230 hours of sunshine a year, fewer than London, despite sitting at 12° south, deep in the tropics. A tropical city, permanently overcast, in a desert.
3. Ten million people drink water that starts as glacier melt above 5,000 metres.
Lima depends on three Andean rivers — the Rímac, Chillón and Lurín — and roughly 80% of its supply comes from the Rímac basin alone. The Rímac rises above 5,000 metres and carries snowmelt and glacial runoff down to a coastal desert.
Retreating Andean glaciers are the long-term risk. In the meantime, fog-catching nets have been strung on hillsides to harvest water from the air, and one engineering university built a billboard that condenses atmospheric humidity into drinking water, storing it in 20-litre tanks.
A city with no rain and 98% humidity has started collecting the humidity.
4. The oldest university in the Americas has been open since 1551.
The National University of San Marcos has operated continuously ever since — longer than any other in the hemisphere.
The clock: Lima sits at about 77° west, on UTC−5, which is built for the 75th meridian. The city runs roughly eight minutes ahead of its own solar noon — very well aligned.
Not that anyone can see it. At 12° south the day length barely moves all year, varying only between about eleven and a half and thirteen hours. Combine a sky that does not change with a sun that is usually behind cloud, and you have a city where the passage of the day is signalled mainly by the grey getting lighter and then darker again.
Sources
- WorldAtlas (~7 mm precipitation per year; second-largest desert city and second-driest capital after Cairo; Humboldt Current and northern rim of the Atacama; metropolitan population of ~9.7 million; San Marcos, founded in 1551, is America's oldest continuously operating university)
- Geography Worlds (10-16 mm per year; three Andean rivers; **~1,230 sun hours per year — less than London**; location 12°S)
- The Andean Post / Aquafondo (~80% of water supply comes from the Rímac basin; Rímac rises above 5,000 meters; more than 10 million people live with less than 10 mm of precipitation)
- EBSCO (average annual precipitation 0.7 cm; garúa)
- ArchDaily / UTEC (Peru's atmospheric humidity reaches 98%; billboard and 20-litre tanks converting humidity into drinking water)
- Longitude calculation: Lima 77.03°W, UTC−5 meridian 75°W → ~8 minutes