Polar vortex weakens unusually early, scientists say

Meteorologists say the polar vortex is weakening unusually early this year, bringing uncertain consequences for winter weather in the Northern Hemisphere.

The polar vortex is a large area of cold, low-pressure air that usually circulates high above the Arctic. In an El Nino year, which 2026 is, it generally weakens near the end of winter, sometimes allowing very cold air to move across Europe and North America from January to March.

Grahame Madge, a spokesperson for Britain's Met Office, said the early-November weakening was “very early” and could be linked to the strength of the El Nino event in the Pacific. He said any temperature impact could be less severe than later in winter because air over Siberia and the Arctic is not yet as cold as it would be by February.

Meteo-France said models point to a major disruption of the upper-atmosphere vortex between 10 and 50 kilometres above the surface in early November. The French weather agency said climate reconstructions dating back to the 1950s show no such disruption before the end of November.

Meteo-France said the potential consequences for France remain highly uncertain and will depend on how the disruption evolves, where it is positioned and whether it reaches lower layers of the atmosphere.

Some research suggests climate change could play a role in polar vortex disruptions, but scientists say the issue remains contested and natural climate variability also plays a role.