Why the coldest places on Earth are defined by a lack of summer heat

Nature · Published 3 October 2026 Swipe more like this →

In short: Polar climates cover over one-fifth of our planet, yet they are defined not by their extreme winter lows, but by their inability to sustain a true summer. From the ice-locked expanses of Antarctica to the treeless tundras of the north, these regions challenge life through persistent cold and unique atmospheric mechanics.

Polar climates are broadly identified by the Köppen classification as regions where no month averages above 10 °C. This threshold is significant because it marks the approximate limit for forest growth. Within this category, scientists distinguish between tundra climates, which see at least one month climb above freezing, and ice cap climates, where temperatures remain below 0 °C year-round. While latitude is the primary driver, elevation creates similar conditions in mountain ranges across the globe, including the Himalayas and the Andes.

The Arctic and Antarctic differ significantly due to their geography. The Arctic is an ocean basin surrounded by land, where sea ice and water moderate temperatures, preventing the North Pole from reaching the extreme lows found in the south. Antarctica, conversely, is a massive, high-altitude continent that acts as the coldest place on Earth. It is also a polar desert, receiving very little annual precipitation because weather fronts struggle to penetrate its interior. The record low of −89.2 °C was documented at Vostok Station in 1983.

Beyond simple temperature averages, polar environments are shaped by complex phenomena like temperature inversions, where air a few thousand feet above the surface can be significantly warmer than the ground. Researchers have long debated how best to quantify these zones. While Wladimir Köppen focused on the 10 °C summer isotherm, others like Otto Nordenskjöld argued that winter conditions are equally vital for plant survival. Later, in 1947, Leslie Holdridge introduced the concept of biotemperature, which ignores temperatures below freezing when calculating the heat available for plant life, providing a more nuanced view of how these harsh climates dictate the boundaries of the living world.

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