BBC Weather has reported that winds in the polar vortex have switched from their typical westerly direction to easterly, marking the "earliest major sudden stratospheric warming on record."
This follows a summer of record-breaking temperatures and heatwaves, with forecasters noting another weather record has now been broken. The previous earliest sudden stratospheric warming (SSW) on record occurred on November 28 in both 1969 and 2025.
What Is Sudden Stratospheric Warming?
Sudden stratospheric warming is a phenomenon where temperatures rise in the stratosphere, causing shifts in the polar vortex—a ring of powerful winds that keeps freezing air near the North Pole. When these winds weaken, Arctic air rushes downwards and often impacts the jet stream. The same process led to the infamous 'Beast from the East' in 2018, which brought 22 inches of snow to some parts of the country.
However, as there are "very few historical examples of early season major SSWs to compare with," BBC Weather says it remains unclear just how the current SSW will impact UK weather. "This event happening so early in autumn is unprecedented in modern observations," forecasters explain.
Current Cold Spell Not Linked to SSW
Temperatures have dropped below freezing this week, reaching -7C in some rural areas overnight, while snow is expected in some regions this weekend. However, this is not a result of SSW. "We do know that it is definitely not connected to the cold spell right now," BBC Weather said. The Met Office previously linked the current conditions to developments in the troposphere, the lowest layer of the atmosphere.
The world is also experiencing a strengthening El Nino, set to be the most powerful in decades. El Ninos have previously been linked with SSW events in the latter half of winter, but BBC Weather says "further research" is needed to draw any links between the current El Nino and the SSW event this week.
Met Office Forecasts Snow for UK
Met Office Deputy Chief Forecaster Steven Keates has said "spells of rain, sleet and some hill snow" are on the cards this weekend. In Scotland, "there is an increasing chance of snow developing later in the day." While most of the snow will be confined to higher ground, he added some "could fall to lower levels too."
"Into next week, unsettled and cold conditions remain with rain, sleet and (mainly hill) snow key features," the Met Office said.
