Kerguelen's climate is oceanic, cold and extremely windswept. Under the
Köppen climate classification, Kerguelen's climate is considered to be an ET tundra climate, in which the warmest month averages below 10 °C, however it is also classified as subpolar oceanic in that the coldest month has an average temperature of above 0 °C. Comparable climates include those of Chilean
Patagonia or
Iceland, as well as other subantarctic island groups such as the
Crozet or
Falkland islands.
All climate readings come from the
Port-aux-Français base, which has one of the more favourable climates in Kerguelen due to its proximity to the coast and its location in a gulf sheltered from the wind.
The average annual temperature lies at around 4.9 °C with an annual range of around 6 °C. The hottest months of the year include January and February, with average temperatures between 7.8–8.2 °C, and the coldest month of the year is August with an average temperature of 2.1 °C. Absolute annual highs in temperature rarely surpass 20 °C, while temperatures in winter have never been recorded to go below −10 °C at sea level.
Kerguelen receives frequent precipitation, with snow throughout the year as well as rain. Port-aux-Français receives a modest amount of precipitation (708 mm per year) compared to the west coast which receives an estimated three times as much precipitation per year.
The mountains are frequently covered in snow but can thaw very quickly in rain. Over the course of several decades, many permanent glaciers have shown signs of retreat, with some smaller ones having disappeared completely.
The west coast receives almost continuous wind at an average speed of 35 km/h, due to the islands' location in the
Roaring Forties. Wind speeds of 150 km/h are common and can even reach 200 km/h.
Waves up to 12–15 m high are common, but there are many sheltered places where ships can dock.