The World Meteorological Organization has declared that El Niño is now "firmly established" and warned the climate pattern is intensifying rapidly, with forecasters giving an almost 100 per cent likelihood it will drive extreme weather worldwide until at least February. The naturally occurring cycle, in which Pacific sea surface temperatures rise well above average, is expected to trigger floods, drought and extreme heat across the globe, and could bring a colder, wetter and stormier autumn and early winter to the UK, according to the Met Office. UN Secretary-General António Guterres said the phenomenon was "being supersized before our eyes" and warned the world was entering "the danger zone of extreme weather".

Scientists say Pacific Ocean temperatures are already more than 2C above average in some regions, with underwater areas reaching as much as 8C above normal. The WMO expects above-normal temperatures across almost all land areas between September and November, with El Niño's effects typically peaking between November and February and often felt most strongly the following year. WMO Secretary-General Celeste Saulo said the event had "the potential to deliver a massive blow to communities and economies", while UK forecasters warned that shifts in the jet stream driven by the warming could send storms towards Britain this winter.