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Live forecasts update automatically; written guidance last reviewed 16 June 2026 by the Playlister UK weather desk. Data from national met services via Open-Meteo.
Sudden stratospheric warming (SSW) is a rapid temperature rise in the polar stratosphere that can disrupt the jet stream, often leading to cold snaps or blocked weather patterns across the UK. This phenomenon typically occurs in late winter or early spring, with notable events recorded in 2018, 2021, and 2025.
How does a sudden stratospheric warming happen?
SSW begins when large atmospheric waves (Rossby waves) travel up from the troposphere and break in the stratosphere, compressing and warming the polar vortex. The vortex can weaken, split, or even reverse direction, allowing cold Polar air to spill southwards.
- The normal westerly winds circling the Arctic are disrupted or reversed.
- Warming in the stratosphere can be as high as 50°C in a few days.
- The effects typically reach the UK surface one to three weeks later.
What consequences does SSW have for UK weather?
A disrupted polar vortex often shifts the jet stream south, increasing the chance of sudden stratospheric warming consequences such as prolonged cold spells, heavy snow, and blocked weather patterns across Britain.
- Not every SSW leads to a UK cold snap; some reverse quickly or are too weak.
- Major SSW events (e.g. February 2018) brought widespread snow and the “Beast from the East”.
- Late-winter SSW events can delay spring warmth and prolong frosts.
For the 10 Day Weather Forecast UK, keep an eye on model changes after a major SSW. The Cold Weather Payment Checker can help if persistent cold follows.
Can a sudden stratospheric warming cause snow in the UK?
Yes. By pushing the jet stream south and allowing Arctic air to flood Europe, SSW often triggers widespread snow and prolonged cold. The latest on sudden stratospheric warming events in 2025 and 2026 shows this pattern remains a key winter risk for Britain.
How long does an SSW event last?
The stratospheric disruption itself typically persists for 10–20 days, but its surface effects can last two to four weeks. Dates of influence vary; check the list of sudden stratospheric warming events for historical durations.
Is sudden stratospheric warming becoming more frequent?
Current research does not clearly link SSW frequency to climate change, though some models suggest a slight increase in certain scenarios. What causes sudden stratospheric warming is still an active area of study, with natural variability playing a dominant role.