An "unprecedented" El Niño could bring wetter, stormier weather to the UK this autumn and early winter.
The global climate event, currently developing in the Pacific, is the largest of its kind in living memory and is expected to have widespread impacts far beyond the tropics, according to experts at the Met Office.
Professor Adam Scaife, head of long range forecasting at the Met Office, said: "We should be clear that this is an unprecedented event.
"I have never seen an El Niño signal this intense in our forecasts."
"This implies that if the forecast is accurate – and other forecast systems show similar extreme values – then 2026 will far exceed our recent experience of El Niño and its worldwide climate influences."
El Niño occurs when equatorial Pacific sea surface temperatures rise significantly.
Typical events see increases of 1°C to 2°C, but current predictions show temperatures in the Nino3.4 region could exceed 3°C in the coming months.
The event is expected to peak during the northern hemisphere winter.
El Niño events disrupt global weather patterns, including rainfall and storm activity.
Tropical regions often experience the most significant effects, but mid-latitude areas are also affected.
In the UK, the Met Office expects the event to raise the likelihood of wetter and stormier weather during the autumn and early winter months.
El Niño also tends to increase global average temperatures.
Dr Nick Dunstone of the Met Office said: "During large El Niño events significantly more heat is released from the ocean to the atmosphere leading to an increase in global average temperature, particularly in the calendar year following the winter peak of the El Niño. Hence, 2027 is very likely to replace 2024 as the warmest year on record and be another year to temporarily exceed +1.5 C above the preindustrial period."
The Met Office states it is continuing to monitor the event closely.
Professor Stephen Belcher, chief of science and technology at the Met Office, said: "This summer we have experienced heat waves across Europe reminding us of the effects of climate change, this large El Niño is a reminder that natural variations in the climate system are also at play, adding to the stresses of climate change."
Further updates are expected later in the year as the El Niño develops.
