מזג האוויר בקוסקו בדצמבר

Forum posters are consistent that December sits right at the start of the wet season (December through February are the wettest months), so a mostly-overcast, roughly 50%-chance-of-rain-on-any-given-day pattern is the norm rather than the exception. The typical shape of a December day: some rain for a couple of hours in the morning or afternoon, then clearing to sun, with an all-day washout called unlikely even if grey skies are close to guaranteed. Daytime highs run cool-ish (60sF) with lows dropping into the high 40sF, and a proper rain jacket plus shoes with good grip are treated as essential packing rather than optional given the regularly slick trail and cobblestone conditions this time of year.

Cusco-forum threads on a January visit describe this as genuinely the wettest month, posters naming rain on most days though rarely lasting the entire day. Regulars call mornings genuinely clearer, several posters naming afternoon and evening as when rain more commonly arrives. Posters call the rainy season genuinely running October or November through March or April, several regulars naming January and February as the heaviest stretch within that window. Regulars call fewer tourists a real upside of visiting in January despite the rain, several threads naming this a genuine tradeoff for anyone willing to pack accordingly. Posters recommend real waterproof layers and flexible daily plans, several regulars calling this standard given how reliably afternoon rain shows up this time of year. The record: 19.9C days, 8C nights, an extraordinarily high 206.1mm across 27 days and 79 percent humidity.

Cusco-forum threads on packing for October describe layering as genuinely the right approach, posters recommending a packable jacket with a hood alongside warmer pieces for cold mornings and nights. Regulars call October the tail end of the region's clear season, sunny midday hours typical even as some sources flag an earlier onset of showers than in previous decades. Posters call sunshine hours genuinely high this month, around ten hours a day on average with better odds early in October than late. Regulars call ticket prices considerably lower than the August peak, a real advantage for anyone flexible on exact dates. Posters recommend discussing altitude medication with a doctor before travel, one traveler specifically mentioning Diamox given concerns about elevation. The record: 21.5C days feeling like 22C, 7C nights, an extraordinarily high 83.7mm across nearly 19 days and 63 percent humidity.

Cusco-forum threads on June weather confirm it's the heart of the dry season and genuinely the most reliable stretch of the year for Machu Picchu and the Sacred Valley, mornings and nights cold enough to drop right near freezing at this altitude even as midday turns bright and comfortably warm once the sun is fully up. Posters describe a consistent daily arc - a cold start, a pleasant midday window from roughly mid-morning to mid-afternoon, then a fast temperature drop as soon as the sun goes behind the hills. Layering is called essential rather than optional, since the swing between the coldest and warmest parts of the day is large even by mountain standards. Regulars call June through August the most crowded months precisely because the weather is this dependable. The record: 20C days feeling like 18C, 2.2C nights, 62 percent humidity, a clean 28 AQI and 10 hours of sun.

Cusco-forum threads on September weather describe it as sitting at the transition out of the dry winter season, days typically clear and sunny with only the occasional passing shower, though posters flag it as a genuine shoulder month between the reliably dry winter and the wetter spring that follows. The defining feature repeated across every thread is the day-to-night temperature swing at this altitude - a comfortable jacket-optional afternoon giving way to a night that can drop well below zero. The standing packing advice is layers built around that swing: light clothing for midday activity, a proper warm layer for evenings regardless of how mild the day felt. Regulars call September a strong month overall for trekking and sightseeing before the rainier months arrive. The record: 21.6C days feeling like 21C, 5.6C nights, 31mm across 10.3 days, a dry 62 percent humidity and 10.8 hours of sun.