A major sudden stratospheric warming (SSW) event is "now likely", according to forecasters - and could bring the return of bitterly cold conditions before spring.
OK, so this SSV event happened before Beast From The East and it is now likely again. Or maybe unlikely. This could bring colder weather, or maybe not. If it does happen, it is likely to be before Spring. So that's before March 21 - June 21. However these SSV systems are not guaranteed and don't happen every year. When it does happen it doesn't always affect the weather. Or sometimes it does. If it does happen, it might not affect Europe but could or could not affect China. Or North America. If it does affect Europe, it could just affect Central and Eastern Europe. Or Wales.
Anyway if it does happen it'll be all down to Climate Change. Or Global Warming.