Except for Tumbes and Piura, which have tropical climates, it rarely rains in Lima or along the coast. The highland parts are frequently bright during the day but freezing at night from June through September. This is the peak season for tourists and the greatest time to visit most locations.
Lima has a dry climate with little precipitation except in Tumbes and Piura, which have tropical climates. The ocean keeps Lima's weather cool and stable, so flooding is not an issue.
The rainy season is between May and October. The best times to visit are during these months if you can handle the heat; otherwise, come during the cooler months.
In Lima, it never rains. The chilly Humboldt current from the South Pole hinders evaporation from the ocean, while the eastern slopes of the Andes block most of the rain-laden clouds from the Amazon, which release their water into the Selva Alta, or "high jungle," a rain forest ecosystem.
The only time it does rain is when one of these two conditions is met: when the Humboldt current weakens or disappears, or when the mountains on its east side disappear (such as at Cape Horn). Then there would be more monsoon activity in Peru.
Lima has been called the sunniest city in the world because over 90 percent of its annual sunlight exposure is due to direct sunlight. Only St. Petersburg, Russia, and Honolulu, Hawaii, receive more daily solar radiation. However, only 5 percent of that is reflected back out to space because the remaining 95 percent is absorbed by the atmosphere and soil. Plants need this energy for photosynthesis and respiration, so they don't reflect any light back out to space.
Also, Lima is on the equator, so it doesn't get cold at night like cities farther away from the sun's rays can. Nighttime temperatures rarely drop below 50 degrees F (10 degrees C), even during the winter months.
Rainfall is also very low compared with other parts of Peru and much of Latin America.
The rainy season is both the hottest and wettest season in Peru. Because to the regular rainfall in the highlands and forest, several of the key pathways for hikers, including most of the Machu Picchu hikes, such as the Salkantay trip, are blocked. During this time, travel is discouraged because many roads are too wet to safely drive or walk.
The rainy season starts around April or May and ends around October or November. Flooding, mudslides, and road closures can occur at any time of year, but these are the biggest dangers when it's raining heavily.
Some locations see up to 300 millimeters of rain over a 30-day period during the rainy season. For comparison, that's about one inch more than the average annual rainfall in Los Angeles, California. The downpours can cause landslides and flooding, which can close roads and disrupt transport links.
Locals call this time of year "marzo cerrado" (closed March). The official warning signal is if there are heavy rains and strong winds together, which can happen within an hour. When this happens, local authorities will issue a "red alert". This means people should avoid going out into the street and allow themselves enough time to reach safety if needed.
During the rainy season, it's best to stay in populated areas with good food and water supplies.
From January to April, there are around 6 hours of daylight every day, but just one hour from July to September. Here are the average number of daylight hours every day. The sea in Lima is never truly warm, however it does get swimmable from January to March.
The average annual rainfall in Lima is about 44 inches or 1100 millimeters. It falls as snow and ice in winter, while summer temperatures often reach 40 degrees Celsius or 105 degrees Fahrenheit.
Lima has a humid subtropical climate, with mild winters and hot summers. Monsoon seasons occur primarily in summer and early fall, when winds coming off the ocean carry moisture from the clouds that form in the west. Winters are dry but cold, with frequent light rainstorms and windy conditions. Summers are wetter than winters, with frequent thunderstorms and high humidity.
Lima is located at an altitude of 12 meters or 39 feet above sea level. This means that although the city is well watered by lakes and rivers, its atmosphere is generally thin and oxygen-poor. This is because air travels faster at higher altitudes, which causes it to be more depleted of oxygen. This problem is usually not a concern for people who don't spend much time indoors, since they wouldn't experience any benefits from having more oxygenated blood.
Lima is the least sunny city in South America from June to November, and the overall quantity of sunlight each year (1,230 hours) makes it the least sunny city on the continent.
Lima has a desert climate, with very hot summers and cool winters. The rainy season is spring and early summer, with an average of 70 inches (1700 mm) recorded over that period. There is also some rain during autumn and winter, but not enough to be considered part of the wet season.
Winters are cold with frequent thunderstorms and dry periods. Spring and fall are the most pleasant seasons, with mild temperatures and little rainfall. Summer can be very humid if you don't use air conditioning.
The best times to visit Lima are between April and October, when the weather is relatively stable and not too hot or cold. If you want to see flowers, go in May or June; if you want to see stars, go in September or October; if you want to party, go in March or April.