Lima has the most counterintuitive climate in South America. It is a coastal city right in the tropics, just 12 degrees south of the equator, surrounded by ocean to the west and desert to the east, and yet it has one of the grayest and most humid skies on the continent for much of the year. Travelers who arrive in July or August expecting a sunny Latin American capital instead find a city covered by a low layer of clouds that can last for entire weeks without breaking. Understanding why that happens makes a trip to Lima much easier and helps plan it better.
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The culprit: the Humboldt Current
The cause of Lima’s climate is oceanographic. The Humboldt Current, also called the Peru Current, is a mass of cold water that rises from Antarctica along the western coast of South America until it reaches the coasts of Ecuador and Peru. The water that washes Lima’s beaches can drop to 14 or 15 degrees Celsius in the middle of winter, much colder than would correspond to that tropical latitude.
When the warm air coming from the Pacific Ocean comes into contact with that mass of cold water, it cools in the lower layers and condenses into fog and stratified clouds that remain suspended at low altitude over the coast. That layer of clouds, which Limeños call garúa, is too low and thin to produce significant rain, but it is enough to cover the sky for months without clearing. The result is a humid, gray, sunless climate unlike any other tropical climate in the world.
The two periods of the year
Lima has two well-defined climate periods, although neither one is what most travelers would expect from a tropical city.
Lima’s summer runs from December to April. In those months the temperature rises, the sky clears, and Lima receives direct sunlight for weeks or months. Temperatures in Miraflores and along the coast range between 20 and 30 degrees Celsius on the warmest days of January and February. The beaches of the Costa Verde fill with Limeños, the Miraflores boardwalk has the liveliest atmosphere of the year, and the sunset over the Pacific produces the most intense colors. It is the best time to visit Lima if the goal is to enjoy the city in good weather.
Lima’s winter runs from May to November, with the grayest period concentrated between June and September. The garúa covers the sky with a layer of low clouds that can remain continuous for weeks. The temperature drops to a range between 12 and 18 degrees Celsius in the coldest months of July and August. It does not have the intense cold of Andean cities: there is no snow, no frost, and no below-freezing temperatures. But the humidity combined with low temperatures and the absence of sun produces a damp cold that is felt in the bones more intensely than the numbers on the thermometer suggest.
Garúa: rain that does not get you wet
Garúa is Lima’s most characteristic weather phenomenon and one of the hardest to explain to someone who has not experienced it. It is not rain. It is moisture so dense in the air that it seems like drizzle but does not produce drops large enough to noticeably soak clothing. Limeños walk under the garúa without umbrellas because technically it is not raining, although after an hour on the street clothes have accumulated enough moisture to be hard to ignore.
Garúa also does not produce the dramatic overcast skies of rainy cities. Lima’s winter sky has no storms, lightning, or dark cumulonimbus clouds. It has a uniform layer of low light-gray stratus clouds that covers the entire horizon like an unchanging ceiling. That uniformity is what makes Lima’s winter psychologically heavier than the cold of Cusco, which may be more intense numerically but has sunshine and blue skies.
Why it almost never rains in Lima
Lima is technically one of the cities with the least precipitation in the world for its size, which is paradoxical given the permanently humid appearance of its climate. Annual precipitation in Lima is only about 10 to 12 millimeters per year, comparable to the driest deserts on the planet. The Andes mountain range acts as a barrier that blocks the passage of humid air masses from the Amazon toward the coast, and the cold Humboldt Current prevents the clouds that form over the ocean from having enough thermal energy to produce significant precipitation.
The result is a paradoxical coastal desert: there is moisture in the air, there are clouds, there is garúa, but there is no rain. The plants along the Miraflores boardwalk and the gardens of the Larco Museum need artificial irrigation to survive even though they are just meters from the ocean. The Atacama Desert, the driest in the world, begins practically where Lima ends to the south.
The exception: El Niño
The El Niño climate cycle drastically alters Lima’s usual pattern. In years of strong El Niño, the ocean temperature rises significantly because the warming of the equatorial Pacific waters displaces or weakens the Humboldt Current. When that happens, Lima can receive intense rains that its infrastructure, designed for the desert, is not prepared to handle. The El Niño episodes of 1983, 1997-1998, and 2017 produced floods, landslides, and significant material damage in Lima in areas that under normal conditions do not see a drop of rain for years.
For the traveler planning a visit, El Niño is an unpredictable variable that in years of a strong cycle can considerably alter the climate conditions of Lima and the entire Peruvian coast.
What to bring depending on the time of year
To visit Lima in summer between December and April, light summer clothing, sunscreen, and sunglasses are enough. The sun in Lima at that time is intense even though the coastal air makes it seem milder than it really is. Sunscreen is essential even if the day looks cloudy because UV radiation passes through the layer of thin clouds more than most visitors expect.
To visit Lima in winter between June and September, it is a good idea to bring a light jacket or a fleece for the nights and mornings, layered clothing that allows you to adapt to temperature changes between indoors and the street, and the mental readiness not to see the sun for several days. An umbrella is useful for the garúa although many Limeños consider it unnecessary.
Gray Lima is not a worse Lima
Winter Lima, with its garúa sky, has its own atmosphere that summer Lima does not have. The museums, food markets, historic center, Creole cuisine restaurants, and the city’s cultural life work just as well or better in winter than in summer because travelers feel less pressure to make the most of the sunshine and are more willing to go indoors. Lima’s gastronomy, which is the most sustainable attraction of the trip regardless of the climate, does not depend on sunshine to be what it is.
What Lima loses in winter in terms of boardwalk, beach, and sunset, it gains in a calmness in the tourist atmosphere that summer does not have. Anyone going to Lima mainly to eat, visit museums, and understand the city’s history can go at any time of year without missing what is essential.