Weather in Cusco in September

Prime time. If you get to pick your dates, September is the one. Highs average 18.4 °C, lows 6.4 °C, and rain falls on 5 days — nothing in the month is working against you.

September ranks 4 of 12 in Cusco: past the worst of the year but short of August, which is the month to book if the dates are open.

Rain falls on only 5 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average September reaches 30 °C. Across the twenty years measured, the hottest September day reached 23.6 °C and the coldest night fell to 1.8 °C.

September is moderately variable: 3 mm in the driest year against 36 mm in the wettest, around an average of 18 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 7.8 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 72%.

How September sits in the year

Temperatures hold steady either side: 18.2 °C in August, 18.4 here, 18.4 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 6 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in September

Cusco sits close enough to the equator that daylight barely moves all year — 12 hours in September, against a range of just 1.6 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

An inland climate

Despite being inland, the year stays fairly even: 13.5 °C between the year's warmest afternoons and coldest nights. At 3312 m, altitude is doing as much work here as latitude: thinner air means fierce sun by day and heat that leaves the moment it sets.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead. If the dates are flexible, April is the trade worth considering — 14 points weaker on weather, and materially quieter.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Cusco versus nearby

If Cusco is one option among several, the nearby comparison is worth making. Arequipa is a better bet in September — 7.7 °C warmer, 4 days less rain. Lima is close enough to be a coin toss — 10.3 °C warmer, 5 days less rain.

So: September is effectively as good as it gets here — 4 points behind August, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Cusco

See all twelve months in Cusco, or where else to go in September.