Sudden Stratospheric Warming Explained
Home › Weather › Sudden Stratospheric Warming Explained
Live forecasts update automatically; written guidance last reviewed 14 June 2026 by the Pressorbit weather desk. Data from national met services via Open-Meteo.
Sudden stratospheric warming (SSW) is a rapid rise in temperature over the Arctic stratosphere that can weaken the polar vortex, increasing the likelihood of cold weather across the UK two to three weeks later. It does not guarantee a freeze, but it shifts the odds significantly.
What is sudden stratospheric warming?
Sudden stratospheric warming happens when large-scale atmospheric waves – triggered by strong weather systems in the lower troposphere – rise into the stratosphere and break. This decelerates or reverses the westerly winds of the polar vortex, sometimes splitting it into two or more lobes. The result is a dramatic warming of the polar stratosphere, often by 40–50°C in a matter of days. This disruption can then propagate downward, altering the jet stream and allowing cold Arctic air to spill southwards over the UK. Understanding what causes sudden stratospheric warming is key to forecasting whether a cold snap is on the horizon.
How does sudden stratospheric warming affect UK weather?
The polar vortex is a band of strong westerly winds that normally keeps cold air locked over the Arctic. When an SSW occurs, that vortex weakens or breaks apart. The jet stream – which steers our weather – often responds by taking on a more meandering, north-south pattern. This can pull freezing air from Siberia or Scandinavia across the UK, bringing sharp frosts and heavy snowfall. The UK Weather Warnings page provides live alerts for such events. The latest on sudden stratospheric warming is usually issued by the Met Office within days of a predicted event, giving time to prepare.
Recent and upcoming events
In early 2025, a major sudden stratospheric warming occurred in January, leading to a notable cold snap in the UK during February. Forecast models for later winter 2025/2026 suggest a moderate risk of further events, though precise dates remain uncertain. A comprehensive list of sudden stratospheric warming events shows that they are most common from December to March, with the strongest impacts felt when the vortex splits rather than simply shifts. If you are tracking the 10-day forecast, remember that SSW effects typically lag by two to three weeks.
Frequently asked questions about sudden stratospheric warming
How long does a sudden stratospheric warming last?
The stratospheric warming itself typically lasts for a week or two, but the disruption to the polar vortex can persist for several weeks. The downstream effects on UK weather – colder conditions and a higher chance of snow – may linger for up to a month after the event.
When is the next sudden stratospheric warming expected in the UK?
Forecasts for sudden stratospheric warming 2026 are not yet reliable, but climatological patterns suggest a possibility from late January onwards. The Met Office issues outlooks for sudden stratospheric warming uk events about two weeks ahead. For real-time updates, check the UK weather hub.
Can sudden stratospheric warming be predicted accurately?
Medium-range models can forecast the initial warming of the stratosphere about 8–10 days in advance. However, the exact consequences at the surface – whether the UK actually gets a freeze – remain uncertain until much closer to the time. This is why the live forecast above should be your first port of call.
