How we know: Sources are listed at the end. Weather figures are climate normals; trail, entry and route facts come from the cited travel-guide and airport pages. Wildly does not publish fare averages in prose; live prices are on the linked route pages.
Peru has three climates stacked side by side: a desert coast where Lima sits under grey fog for half the year, the Andes with a sharp wet–dry cycle, and the Amazon, which is hot and wet all year. Because almost every first trip is built around Cusco and Machu Picchu, the Andean calendar is the one that matters. The dry season from May to September is the time to go, with May and September the sweet spots before and after the June–August crowds. The wet season runs November to March, and the Inca Trail is closed for the whole of February.
Cusco weather by month
Climate normals for Cusco's Alejandro Velasco Astete airport, elevation 10,660 ft (3,249 m):
| Month | Avg high | Avg low | Rain | |---|---|---|---| | January | 69°F (20°C) | 46°F (8°C) | 6.0 in | | February | 69°F (20°C) | 46°F (8°C) | 5.2 in | | March | 69°F (20°C) | 46°F (8°C) | 4.2 in | | April | 70°F (21°C) | 43°F (6°C) | 1.5 in | | May | 70°F (21°C) | 38°F (4°C) | 0.3 in | | June | 69°F (21°C) | 35°F (2°C) | 0.1 in | | July | 69°F (21°C) | 34°F (1°C) | 0.2 in | | August | 71°F (22°C) | 37°F (3°C) | 0.3 in | | September | 71°F (22°C) | 41°F (5°C) | 0.7 in | | October | 71°F (22°C) | 44°F (7°C) | 2.1 in | | November | 72°F (22°C) | 46°F (8°C) | 3.0 in | | December | 70°F (21°C) | 46°F (8°C) | 4.9 in |
Daytime highs barely change all year; what changes is rain and night-time cold. June and July are almost rain-free but nights drop to near freezing, and it is colder still on the trail at 13,000 ft. January is the wettest month. Machu Picchu itself, at about 8,000 ft in the cloud forest, is warmer and wetter than Cusco in every month.
The Inca Trail closes in February
Wikivoyage's Inca Trail guide states plainly that "the trail is closed in February" for maintenance and clean-up, and the Cusco guide repeats it. Machu Picchu remains open by train in February, and alternative treks such as the Salkantay and Lares routes still run, but if the classic four-day trail is the point of your trip, February is out.
Permits are the other constraint. Daily numbers on the trail are capped (the cap includes guides and porters, so actual trekker places are fewer), and the guide advises that for popular dry-season dates you should arrange the trek "six months or more in advance." Its own pick for the best month is May: dry and sunny, vegetation still lush from the rains, and before the high-season crowds and coldest nights. It warns against November to March for cloud, rain, slick rock and landslide risk.
Season by season
May–September (Andean dry season, peak). Clear skies, cold nights, the best trekking and the clearest views from Machu Picchu. June through August is high season: Inti Raymi, the Inca sun festival, fills Cusco on June 24 (Wikivoyage, Cusco), and the northern-hemisphere summer holiday brings the year's biggest crowds. May and September have nearly the same weather with noticeably fewer people.
October–November (shoulder). Rain returns gradually; October is often still fine, and the landscape greens up. Good value, fewer trekkers, some afternoon showers.
December–March (Andean wet season). Heavy afternoon rain, muddy trails, occasional landslides that disrupt the Machu Picchu train. The Inca Trail is closed in February. Compensations: low season prices, green mountains, and the coast is at its sunniest. Carnival in February is lively across the highlands.
April (early dry). Rain tapering off, everything green, permits easier to find than in May. A good compromise for anyone who cannot travel in the core dry months.
The coast and the Amazon
Lima runs on the opposite schedule. Wikivoyage notes the coastal garúa, a persistent grey fog, sits over the city from roughly May to November, exactly when the Andes are clearest; Lima's summer (December–March) is warm, sunny and humid. It almost never rains in Lima in any month. The Amazon (Iquitos, Puerto Maldonado, Manu) is hot and wet year-round with somewhat drier conditions from roughly May to October; river levels are highest early in the year.
Altitude: plan your first days around it
Cusco sits at about 11,150 ft (3,400 m), and Wikivoyage's warning that altitude sickness, or soroche, "has the potential to develop into something extremely dangerous" is worth taking seriously. Sensible sequencing: fly Lima–Cusco, then drop straight down to the Sacred Valley (Ollantaytambo and Urubamba are around 9,000 ft) for the first two nights, visit Machu Picchu at about 8,000 ft, and return to Cusco once acclimatised. Take it easy on day one, drink water, go light on alcohol, and talk to your doctor about acetazolamide if you have had trouble before. Good acclimatisation is, in the guide's words, "absolutely necessary" before any high trek.
Getting there from the US
Lima's Jorge Chávez International (LIM) is the gateway; all Cusco flights connect there. Per the airport's destinations table, nonstops from the US include Miami (American, LATAM Perú and Sky), Atlanta (Delta and LATAM Perú), Houston (United), Newark (United, with an end date noted in the table), New York–JFK (LATAM Perú), Los Angeles (LATAM) and Salt Lake City (Delta, seasonal). Other cities connect through those hubs or through Bogotá and Panama City.
Flight time from Miami is about 5.5 hours, 8 from New York or Atlanta and 8.5 from Los Angeles. Lima's time zone matches the US East Coast in winter, so jet lag is minimal. For today's prices see Miami to Lima, JFK to Lima, LAX to Lima and Atlanta to Lima. Budget a separate Lima–Cusco ticket; several Peruvian carriers fly it many times a day.
When fares tend to be lowest
Demand on US–Peru routes peaks with the Andean dry season, June through August, when North American summer holidays and Machu Picchu's best weather line up, and again over Christmas and New Year, when Peruvians abroad fly home. The quiet months for airfare are the Andean wet season, roughly February to April excluding Easter, and October–November. May and September, the best months on the ground, sit between the two.
That is a demand-calendar argument, not a price forecast. Fares on any specific route depend on capacity and competition, so pick your window, check the route page for what it is actually pricing today, and set a price alert with a target you would be happy to pay. Wildly checks the route daily and emails you when the fare drops.
Entry requirements for US citizens
US passport holders do not need a visa for tourism; Wikivoyage lists the US among countries whose citizens may receive entry on arrival for up to 183 days, with the immigration officer setting the actual number of days. Your passport should be valid for at least six months. Ask a travel clinic about yellow fever vaccination if your itinerary includes the Amazon; confirm current entry rules with the Peruvian consulate before travel, and note that Machu Picchu entry tickets are timed and limited, so buy them before you fly.
FAQ
What is the best month to visit Machu Picchu? May or September: dry-season weather without the June–August crowds. Wikivoyage's Inca Trail guide names May as the best month for the trek.
When is the Inca Trail closed? For all of February, for maintenance (Wikivoyage). Alternative treks and the train to Machu Picchu still operate.
How far in advance do Inca Trail permits sell out? For dry-season dates, book six months or more ahead per Wikivoyage. Shoulder months are easier but still not last-minute.
Is the rainy season a bad time to visit Peru? For trekking, yes. For Lima, the coast and lower prices, it is the best time. Machu Picchu is open year-round outside trail closures; expect rain and cloud between December and March.
How bad is the altitude in Cusco? Cusco is about 11,150 ft. Most people feel it. Spend your first nights lower in the Sacred Valley and go easy for 48 hours.