Patagonia - Climate

Climate

Overall climate is cool and dry. The east coast is warmer than the west, especially in summer, as a branch of the southern equatorial current reaches its shores, whereas the west coast is washed by a cold current. However, winters are colder on the inland plateaus east of the slopes and further down the coast on the south east end of the Patagonian region. For example at Puerto Montt, on the inlet behind Chiloé Island, the mean annual temperature is 11 °C (52 °F) and the average extremes 25.5 °C (77.9 °F) and −1.5 °C (29.3 °F), whereas at Bahía Blanca near the Atlantic coast and just outside the northern confines of Patagonia the annual temperature is 15 °C (59 °F) and the range much greater, as temperatures above 35 °C and below −5 °C are recorded every year. At Punta Arenas, in the extreme south, the mean temperature is 6 °C (43 °F) and the average extremes 24.5 °C (76.1 °F) and −2 °C (28 °F). The prevailing winds are westerly, and the westward slope has a much heavier precipitation than the eastern in a rainshadow effect; the western islands close to Torres del Paine receive an annual precipitation of 4,000 to 7,000 mm, whilst the eastern hills are less than 800 mm and the plains may be as low as 200 mm annual precipitation.

Precipitation is highly seasonal in northwestern Patagonia (for example, Villa La Angostura, in Argentina and right next to Chile, receives up to 434 mm of rain and snow in May, 297 mm in June, 273 in July, compared to 80 in February and 72 in March. The total for the city is 2074 mm, making it one of the rainiest in Argentina. Further west, some areas receive up to 4,000 mm and more, especially on the Chilean side. In the northeast, the seasons for rain are reversed: most rain falls from occasional summer thunderstorms, but totals barely reach 500 m in the northeast corner, and rapidly decrease to less than 300 mm. The Patagonian west coast, which belongs exclusively to Chile, has a cool oceanic climate, with summer temperatures ranging from 14 °C in the south to 19 °C in the north (and nights between 5 °C and 11 °C) and very high precipitation, from 2,000 to more than 7,000 mm in local micro-climates. Snow is uncommon at the coast in the north, but happens more often in the south, and frost is usually not very intense.

Immediately east from the coast are the Andes, cut by deep fjords in the south and by deep lakes in the north, and with varying temperatures according to the altitude. The tree line ranges from close to 2,000 m on the northern side (except for the Andes in northern Neuquen in Argentina, where sunnier and dryer conditions allow trees to grow up to close to 3,000 m), and diminishes southward to only 600–800 m in Tierra del Fuego. Precipitation changes dramatically from one spot to the other, and diminishes very quickly eastward. An example of this is Laguna Frías, in Argentina, receives 4,400 mm yearly. The city of Bariloche, about 40 km further east, receives about 1,000 mm, and the airport, another 15 km east, receives less than 600 mm. The easterly slopes of the Andes are home to several Argentine cities: San Martín de los Andes, Bariloche, El Bolsón, Esquel, El Calafate. Temperatures there are milder in the summer (in the north, between 20 °C and 24 °C, with cold nights between 4 °C and 9 °C; in the south, summers are between 16 °C and 20 °C, at night temperatures are similar to the north) and much colder in the winter, with frequent snowfall (although snow cover rarely lasts very long). Daytime highs range from 3 °C to 9 °C in the north, and from 0 °C to 7 °C in the south, whereas nights range from −5 °C to 2 °C everywhere. Cold waves can bring much colder values: -21 °C have been recorded in Bariloche, and most places can often see temperatures between −12 °C and −15 °C and highs staying around 0 °C for a few days.

Directly east of these areas, the weather becomes much harsher: precipitation drops to between 150 and 300 mm, the mountains no longer protect the cities from the wind, and temperatures become more extreme. Maquinchao is a couple hundred kilometers east of Bariloche, at the same altitude on a plateau, and summer daytime temperatures are usually about 5 °C warmer, rising up to 35 °C sometimes, but winter temperatures are much more extreme: the record is −35 °C, and it is not uncommon to see some nights 10 °C colder than Bariloche. The plateaus in Santa Cruz province and parts of Chubut usually have snow cover through the winter, and often experience very cold temperatures. In Chile, the city of Balmaceda is known for being situated in this region (which is otherwise almost exclusively in Argentina), and for being the coldest place in Chile, with temperatures below −20 °C every once in a while.

The northern Atlantic coast has warm summers (28 °C to 32 °C, but with relatively cool nights at 15 °C) and mild winters, with highs of about 12 °C and lows about 2–3 °C. Occasionally, temperatures reach −10 °C or 40 °C, and rainfall is very scarce. It only gets a bit colder further south in Chubut, and the city of Comodoro Rivadavia has summer temperatures of 24 °C to 28 °C, nights of 12 °C to 16 °C, and winters with days around 10 °C and nights around 3 °C, and less than 250 mm of rain. However, there is a drastic drop as we move south to Santa Cruz: Rio Gallegos, in the south of the province, has summer temps of 17 °C to 21 °C, (nights between 6 °C and 10 °C) and winter temperatures of 2 °C to 6 °C, with nights between −5 °C and 0 °C despite being right on the coast. Snowfall is common despite the dryness, and temperatures are known to fall to under −18 °C and to remain below freezing for several days in a row. Rio Gallegos is also among the windiest places on Earth, with winds reaching 100 km h occasionally.

Tierra del Fuego is extremely wet in the west, relatively damp in the south, and dry in the north and east. Summers are cold (13 °C to 18 °C in the north, 12 °C to 16 °C in the south, with nights generally between 3 °C and 8 °C), cloudy in the south, and very windy. Winters are dark and cold, but without extreme temperatures in the south and west (Ushuaia rarely reaches −10 °C, but hovers around 0 °C for several months, and snow can be heavy). In the east and north, winters are much more severe, with cold snaps bringing temperatures down to −20 °C all the way to Rio Grande on the Atlantic coast. Snow can fall even in the summer in most areas as well.

The depletion of the ozone layer over the South Pole has been reported as being responsible for blindness and skin cancer in sheep in Tierra del Fuego, and concerns for human health and ecosystems.