The Best Time to Visit the Atacama Desert

Most guides answer this with a season. We can answer it with a measured record, because the figures this site publishes come from the Chilean agroclimatic station record for San Pedro de Atacama rather than from a gridded weather model.

That distinction matters more here than it would anywhere else. The two global models we checked put annual rainfall at 77 and 84 mm. The station record says 38 mm. The models average over cells about 30 km wide that take in the Andean slopes east of the oasis, which are far wetter than the valley floor. On a page about the driest desert on Earth, getting that number wrong by a factor of two is getting the subject wrong.

The year in numbers

Month	High °C	Low °C	Rain mm	Humidity	Sunset
January	28.0	8.8	4	28%	20:23
February	28.0	9.4	21	38%	20:12
March	27.0	7.9	7	31%	19:49
April	25.0	5.1	0	23%	18:19
May	21.8	1.9	1	22%	17:59
June	18.9	−0.5	2	20%	17:55
July	19.3	−0.8	0	18%	18:04
August	21.5	0.9	1	14%	18:16
September	23.4	2.7	1	13%	19:26
October	25.7	4.4	0	13%	19:36
November	27.3	5.8	1	17%	19:53
December	28.0	7.3	0	22%	20:13

Two things stand out.

Twenty-one of the year’s 38 mm of rain falls in February. Add January’s 4 mm and March’s 7 mm and those three months hold 84 per cent of the annual total. Everything from April to December is functionally rainless.

The daily temperature swing is about 20 °C in every single month. January runs 28.0 down to 8.8. July runs 19.3 down to −0.8. That constant is the single most useful planning fact on this page, and it is the reason the packing question is not trivial here.

The altiplanic winter

February’s 21 mm and 38 per cent humidity are the invierno altiplánico — the Bolivian winter — when moisture is drawn over the Andes from the Amazon basin and falls as afternoon storms on the high ground.

It does not rain on the town so much as on the routes. The practical consequence is closed roads: El Tatio and the altiplanic lagoons are the first to go, and a tour cancelled for weather in February is a common enough occurrence that operators have refund policies written for it.

It is also peak season, because it is the southern summer holidays.

The answer

September and October. Humidity at its annual minimum of 13 per cent, rainfall of 1 mm and 0 mm, daytime highs of 23 and 26 °C, and night-time lows of 2.7 and 4.4 °C rather than July’s below-freezing. You get the winter sky at autumn temperatures, and sunset has moved back past 19:20 so the days are usable.

April and May are the other honest answer: 0 and 1 mm of rain, mild days, and the altiplanic winter safely finished.

June to August if stargazing is the entire reason you are coming. The humidity is low, the sky is at its most stable — and the nights are genuinely cold, with July averaging −0.8 °C in town and colder at the geysers.

February, if you can avoid it, avoid it. The wettest month, the most humid, the most likely to have your tours cancelled, and the busiest.

The dates nobody mentions

18 and 19 September are Fiestas Patrias, Chile’s national holiday. Domestic tourism peaks, accommodation in San Pedro fills, and prices rise. It sits in the middle of the best weather window, which is an awkward coincidence — book either side of it.

The other Chilean public holidays that fall in good-weather months are 1 May, 21 May, 21 June, 28 June, 16 July and 11 October.

What we will not tell you

A crowd calendar. Producing one needs per-day visitor numbers for San Pedro, and no source publishes them. Guessing would be worse than not having one, so this page gives you the school-holiday and public-holiday pattern instead, which you can check directly and which is what actually drives the crowd.

Once you have a month, the itinerary page covers what to do with the days, and the tours are booked from there.