A major El Niño is building: what could it mean for UK transport resilience?

Changes in ocean temperatures in the tropical Pacific can modify weather patterns across the globe, with effects that extend well beyond the region where they originate. Recent global climate observations indicate that El Niño has re-emerged, is continuing to strengthen, and is likely to persist until early spring 2027. Although it develops thousands of kilometres from the United Kingdom, its influence can extend across the globe, changing weather patterns far beyond where it begins. This raises an important question: what could El Niño mean for the UK’s weather and the transport networks that millions of people rely on every day?  

Under typical conditions, strong trade winds blow from east to west across the tropical Pacific, moving warm surface waters towards Indonesia and allowing cooler water to rise near the coast of Peru. During an El Niño event, these trade winds weaken or, in some cases, reverse (Fig 1a). As a result, warm surface water shifts eastward towards the Americas. This process can substantially change global atmospheric circulation, influencing rainfall patterns, jet streams, and global temperature anomalies.

There are different definitions, but as a guide the El Niño and La Niña episodes occur when anomalies in the “Niño 3.4 region” (5°N-5°S, 120°W-170°W) are larger than about 0.5 °C in magnitude for several months (as in Fig 2). These events occur on average every 2 to 7 years. Typically, El Niño occurs more frequently than La Niña, El Niño typically lasts 9–12 months, and La Niña typically lasts 1–3 years. Both tend to develop during March–June, reach peak intensity during December–April, and then weaken during May–July. However, prolonged El Niño episodes have lasted 2 years, and even as long as 3-4 years.

Strong El Niño events have historically helped drive record-breaking global temperatures, including in 1998, 2016, and 2024.

Recent climate assessments indicate that an El Niño event is intensifying. In practical terms, the following developments are observed and forecast:

• Rapid ocean warming: A substantial area of the central and eastern Pacific is currently recording sea-surface temperatures significantly (~3x SD) above the long-term average (Fig 3).
• Potential for a very strong El Niño: Forecast models and observational data are closely aligned, with scientists estimating a 97% likelihood that the event will continue through early spring 2027. There is also an 81% probability that it will peak as a “very strong” El Niño by the end of the year, placing it among the most significant events ever recorded. Fig. 4 shows ECMWF forecast for the current El Niño development, in terms of SST anomaly in the Niño 3.4 region” (5°N-5°S, 120°W-170°W), exceeding the historical context shown in Fig. 2  later in the autumn and winter this year. This signal has been consistent for the last few month’s forecasts.
• The influence of climate change: The significance of this event is heightened by the fact that it is occurring against a background of long-term, human-induced global warming. The result is a combination of natural climate variability and an elevated baseline climate state.

El Niño’s influence on Europe remains uncertain and difficult to isolate, because it is only one of several drivers of regional weather and its signal can be obscured by other factors. According to the Met Office, strong El Niño events have historically been associated with a tendency for UK winters to show two broad phases:

1. Autumn and Early Winter: During October, November, and December, El Niño can influence the position and behaviour of the Atlantic jet stream, increasing the likelihood of milder, wetter, and windier conditions across the United Kingdom.
2. Late Winter: During January and February, El Niño may contribute to changes in high-altitude atmospheric circulation, including conditions that can affect the polar vortex (Ineson et al., 2026). In some cases, this can reduce the dominance of Atlantic storm systems and increase the likelihood of colder, calmer, and more settled conditions.

This pattern draws attention to a major area of vulnerability: the United Kingdom’s national transport infrastructure.

Road and rail networks in the UK are already sensitive to extreme weather. A very strong El Niño occurring alongside a changing climate could place further pressure on these transport systems.

1. Pressure on the rail network

The United Kingdom’s railway system includes substantial legacy infrastructure, much of which is vulnerable to the intense rainfall that can accompany El Niño-related weather patterns.

• Landslips and earthworks: The United Kingdom has approximately 20,000 km of steep earth slopes and embankments supporting its rail network. When prolonged winter rainfall fully saturates the ground, these embankments can fail. Such failures may cause significant service disruption, damage infrastructure, and, in severe cases, pose safety risks.
• Flooded tracks and financial costs: According to the Environment Agency, more than one-third of the United Kingdom’s rail network is already at risk of flooding. Extreme rainfall can submerge signalling systems and displace the ballast that stabilises railway tracks. Weather-related disruption has already resulted in substantial compensation costs for Network Rail in recent years.
• Increased intensity and duration of low adhesion season: UK railways are particularly susceptible to conditions whereby a combination of wet rails and contaminants e.g. vegetation and leaves reduce the friction between wheel and rail leading to a reduced ability to strop trains amongst other challenges.  Excess rainfall would exacerbate these challenges which result in increased costs and potentially safety risks.

2. Road network risks: potholes, surface water, and bridge scour

Road infrastructure, including the Strategic Road Network and local authority-managed roads, may also face significant challenges under sustained wet conditions leading to road closures.

• Pothole formation: Intense winter rainfall followed by freezing conditions creates favourable conditions for pothole development. Water enters cracks in the road surface, expands when frozen, and progressively weakens the asphalt structure.
• Bridge scour: Bridge scour is a significant but often less visible infrastructure risk. During periods of high river flow, fast-moving water can erode the material surrounding bridge foundations. Many ageing road bridges across the United Kingdom may be vulnerable to this form of structural degradation.
• Reduced performance of drainage systems: These assets are essential to manage surface water on the network. Increased rainfall poses a significant challenge potentially creating additional localised events as well as water ingress to assets leading to structural damage e.g. reinforced concrete bridges.  

In addition to road and rail networks, the aviation sector might also be affected. Increased storms could cause delays in arrivals and departures of flights at key locations such as London Heathrow Airport, for example.

A strong El Niño does not guarantee extreme weather in the United Kingdom, but instead shifts the odds towards conditions that place greater stress on transport infrastructure. As the climate continues to warm, these natural climate fluctuations are increasingly unfolding against a backdrop of rising temperatures and a more energetic atmosphere, amplifying the potential for disruptive weather.

For the United Kingdom, the message is clear: railways, roads, bridges and airports need to be prepared for more frequent and more intense extreme weather events. Severe weather has already become more common, and more costly, and will continue to worsen until fossil fuel emissions reach Net Zero.

Advances in artificial intelligence and machine learning, combined with seasonal climate forecasting, high-resolution climate modelling, Earth observations and real-time infrastructure monitoring, offer unprecedented opportunities to anticipate weather-related disruptions and strengthen transport resilience. Utilising these technologies for early warnings and monitoring of asset resilience, as well as increased maintenance and strengthening of assets, will be key to designing and managing transport networks that can adapt to an increasingly variable and changing climate.

Ineson, S., C. Almond, P. Davies, et al. 2026. “Prediction of European Winter 2023/24: Influence of a Strong El Niño.” Atmospheric Science Letters 27, no. 2: e70006.