2025 Was the UK's Warmest Year on Record. Here Is Why That Changes the Material Specification Conversation.
- May 24
- 10 min read
2025 was the UK's warmest and sunniest year on record. The Met Office has confirmed that extreme heat events are becoming more frequent, and that the UK's infrastructure was not designed for the climate it is now operating in. For engineers and specifiers, this is not a future problem. The material decisions being made on infrastructure today will determine how assets perform in a UK climate that is measurably and irreversibly hotter than the one those assets were designed for.
Published by Reinforce Technology | May 2026
In January 2026, the Met Office confirmed that 2025 had broken two climate records simultaneously — the UK's warmest and sunniest year since observations began in 1884 (Met Office, 2026). The UK's annual mean temperature reached 10.09°C, making it only the second year in the entire observational record where the UK's average temperature has exceeded 10°C. A rapid attribution study by the Met Office found that human-induced climate change has made a temperature of this level approximately 260 times more likely than it would have been in pre-industrial times — but that in the current climate, it could now occur once every three years on average.
The UK is warming at approximately 0.25°C per decade (Royal Meteorological Society, 2025). The most recent decade was 1.24°C warmer than the 1961 to 1990 baseline. In July 2022, Coningsby in Lincolnshire reached 40.3°C — the first time a temperature above 40°C had ever been recorded in the UK. The Met Office's June 2025 study, published in the journal Weather, found that the probability of exceeding 40°C in the UK is accelerating at pace, and that extreme heat events will become longer and more intense in the decades ahead (Met Office, 2025).
The Climate Change Committee's 2025 Progress Report to Parliament was direct about the infrastructure implications: extreme heat disrupts infrastructure systems via rail buckling and power line sagging. The cascading effects of failures can amplify impacts. Water supplies face rising drought risk. Over a third of railway and road kilometres are currently at flood risk, predicted to rise to around half by 2050 (CCC, 2025).
This is the operating environment that UK infrastructure — built and being built now — will face across its 25 to 50-year design life. The question for engineers, specifiers, and procurement teams is straightforward: which materials are designed to perform in that environment, and which ones were designed for a UK climate that no longer exists?
What Rising Temperatures Actually Do to Steel Infrastructure
Steel is the dominant structural and secondary infrastructure material across UK industry. It performs adequately across the temperature range it was designed and specified for. The problem is that the temperature range the UK now experiences — and will increasingly experience — is expanding beyond the assumptions embedded in decades of conventional infrastructure design.
Thermal expansion is the most immediate and well-documented effect of rising temperatures on steel infrastructure. Steel expands by approximately 12 micrometres per metre per degree Celsius of temperature increase (IntechOpen, 2022). At the scale of a large bridge, a railway line, a rooftop solar array, or an industrial platform, this expansion is significant — and if not adequately accommodated in the design, it produces buckling, distortion, and in extreme cases, structural failure. The 2022 heatwave caused rail buckling events across the UK network, with speed restrictions imposed on hundreds of kilometres of track. As peak temperatures increase and heatwave events become more frequent, the thermal stress on steel infrastructure accumulates across more events, over more days, across more years.
At elevated temperatures, steel also experiences changes in its mechanical properties. The yield strength of structural steel begins to reduce noticeably above 300°C, with significant reductions above 400°C (IntechOpen, 2022). For operational temperatures in the range of ambient UK summer heat — even at extremes of 40°C — this reduction is not structurally critical for most primary steel elements. However, for secondary steel infrastructure in enclosed spaces, near industrial heat sources, or exposed to direct sunlight on south-facing surfaces, localised temperatures can exceed ambient air temperature significantly, and the cumulative thermal cycling across heating and cooling events creates fatigue loading that is not typically accounted for in standard secondary infrastructure design assumptions.
Elevated temperatures also accelerate corrosion on galvanised and coated steel. The rate of electrochemical corrosion reactions increases with temperature — meaning that a galvanised steel cable tray or mounting frame in an outdoor industrial environment will corrode faster in the hotter, more humid summers that UK climate projections consistently forecast. The galvanised coating that provided ten years of protection under a cooler, drier UK climate may provide eight or seven years under the climate the UK now experiences — compressing the maintenance cycle and increasing the lifetime maintenance cost of the installation (NACE International, 2016).
The infrastructure being specified today in galvanised steel will operate in a climate where peak temperatures are higher, heatwave events are more frequent, and the thermal stress on materials is greater than at any point in the recorded history of UK infrastructure. That is a relevant input to material selection decisions — and it consistently favours FRP over steel.
How FRP Performs in a Hotter UK Climate
1. Low Thermal Expansion — Dimensional Stability Under Heat
FRP has a significantly lower coefficient of thermal expansion than steel. Glass fibre reinforced polymer expands at approximately 8 to 14 micrometres per metre per degree Celsius longitudinally, depending on fibre orientation and volume fraction — comparable to or lower than steel, and significantly lower than aluminium (IntechOpen, 2022). More importantly, FRP's mechanical properties do not degrade at the ambient temperature extremes that UK heatwaves produce. There is no softening, no yield point reduction, and no structural performance change across the temperature range from UK winter lows to summer highs that steel-equivalent FRP sections are designed for.
For solar farm secondary frames, rooftop cable management systems, and industrial secondary platforms exposed to direct sunlight in summer, the dimensional stability of FRP under thermal loading is a consistent advantage over steel in the hotter UK climate now emerging. Thermal ratcheting — the progressive accumulation of small permanent deformations through repeated heating and cooling cycles — is a documented fatigue mechanism in metal structures subjected to repeated thermal loading. FRP structural profiles in the correct resin system do not exhibit this mechanism in the ambient temperature range of UK climate extremes.
2. Corrosion Immunity Is More Valuable in a Wetter, Humidity-Variable Climate
The Climate Change Committee's 2025 report confirmed that the UK will experience warmer and wetter winters alongside hotter and drier summers — creating a more pronounced humidity cycling pattern across the annual climate (CCC, 2025). This increased seasonality — wetter winters, hotter summers — creates the precise conditions under which galvanised steel coatings degrade fastest: repeated cycles of wet contact followed by accelerated drying, driving moisture into the zinc layer at fixing points and cut edges and initiating corrosion at every location where the coating is thinnest.
FRP has no corrosion mechanism in this environment. Its resistance to moisture, humidity cycling, and the chemical exposure that accompanies wet-dry cycling in outdoor industrial settings is intrinsic to the composite matrix rather than dependent on a surface coating that cycles through wet contact and drying alongside the climate. As UK winters become wetter and UK summers become hotter, the climate is becoming progressively more hostile to galvanised steel infrastructure and progressively more aligned with the environmental conditions that FRP was designed to perform in.
3. UV Stability Is a Specification Requirement, Not a Nice-to-Have
2025 was not just the UK's warmest year on record — it was also its sunniest. UV
radiation is the primary degradation mechanism for the polymer component of standard FRP resins, progressively breaking down surface bonds and causing chalking, cracking, and eventual reduction in mechanical properties if the material is not formulated for UV resistance.
FRP products manufactured for outdoor infrastructure applications — including Reinforce Technology's structural profiles, cable trays, and solar frames — are formulated with UV-stable resin systems that inhibit this degradation mechanism. UV stability is not a coating applied after manufacture. It is built into the resin formulation, providing consistent protection throughout the material's design life without the surface maintenance that UV-exposed polymer coatings on steel require.
As UK sunshine hours increase and UV intensity rises alongside temperature, the distinction between FRP products formulated for outdoor UV exposure and those that are not becomes increasingly significant for long-life infrastructure applications. A solar mounting frame or cable tray exposed to the increasing UV loading of UK summers across a 25 to 30-year operational life will maintain its mechanical properties if correctly specified in a UV-stable FRP system — and will not require recoating or surface treatment at any point in that operational period.
4. Thermal Non-Conductivity — A Practical Advantage in Solar and Industrial Applications
FRP has a thermal conductivity of approximately 0.3 to 0.4 W/mK — roughly one hundred times lower than steel's approximately 50 W/mK (IntechOpen, 2022). In solar farm applications, this thermal non-conductivity means that FRP mounting frames and cable management do not transfer heat from sun-exposed surfaces into the structural elements below, and do not create thermal bridges that accelerate temperature cycling at fixing points and connection interfaces.
In data centre cooling zones, power cable management in high-load runs, and industrial platforms near process heat sources, the lower thermal conductivity of FRP contributes to a more controlled thermal environment for adjacent materials and equipment. As ambient temperatures rise and cooling loads in data centres and industrial facilities increase, the marginal thermal management advantage of FRP secondary infrastructure becomes incrementally more relevant across each year of the asset's operational life.
Designing for the Climate of 2040, Not the Climate of 1990
Infrastructure design codes, material specifications, and engineering assumptions are largely based on historical climate data. The Climate Change Committee's 2025 report made clear that this approach is no longer adequate — that infrastructure now being specified must be designed for the climate of its operational life, not the climate in which its design codes were written (CCC, 2025).
The UK is warming at 0.25°C per decade. An industrial asset specified today and designed for a 30-year operational horizon will spend the majority of its operational life in a climate that is 0.5 to 0.75°C warmer than today's. A 50-year water treatment works will operate its final decades in conditions that are approaching 1°C warmer than current. These are not marginal changes in the context of material performance. They are the difference between a galvanised coating that degrades in 10 years and one that degrades in 8 years. They are additional UV cycles on polymer coatings that were already at the edge of their design performance envelope. They are more frequent and more intense heatwave events that subject steel structures to thermal expansion loads that legacy design codes did not anticipate.
FRP structural profiles, cable management, grating, solar frames, and fencing were designed from the outset for outdoor, corrosive, UV-exposed, thermally variable environments. They do not require the UK climate to stay within historical bounds in order to perform across their design life. They are, in the most direct sense, the infrastructure materials designed for the climate the UK is now entering — not the climate it is leaving behind.
The specification decision that considers climate trajectory — not just current conditions — consistently favours FRP over galvanised steel for secondary infrastructure in outdoor, exposed, and corrosion-intensive environments. And as each year's climate data confirms that 2025 was not an anomaly but an acceleration, that specification argument becomes stronger, not weaker, with time.
Reinforce Technology FRP Products for a Warming UK
Reinforce Technology supplies FRP structural profiles, cable trays, grating, solar frames, perimeter fencing, and drainage systems for outdoor industrial and infrastructure applications across the UK. All products intended for outdoor, UV-exposed applications are formulated with UV-stable resin systems providing long-term dimensional and mechanical stability across the full range of UK climate conditions — including the increasingly extreme summer temperatures and UV intensities that UK climate projections forecast for the decades ahead.
Available in polyester, vinyl ester, and epoxy resin systems to match the specific environmental and chemical exposure of each application. We work with structural engineers, EPC contractors, facilities managers, and procurement teams across solar energy, water treatment, data centre, offshore energy, rail, and general industrial infrastructure. Contact us to discuss your project and the correct FRP specification for the climate your asset will operate in across its full design life.
Reinforce Technology FRP Products for a Warming UK
Reinforce Technology supplies FRP structural profiles, cable trays, grating, solar frames, perimeter fencing, and drainage systems for outdoor industrial and infrastructure applications across the UK. All products intended for outdoor, UV-exposed applications are formulated with UV-stable resin systems providing long-term dimensional and mechanical stability across the full range of UK climate conditions — including the increasingly extreme summer temperatures and UV intensities that UK climate projections forecast for the decades ahead.
Available in polyester, vinyl ester, and epoxy resin systems to match the specific environmental and chemical exposure of each application. We work with structural engineers, EPC contractors, facilities managers, and procurement teams across solar energy, water treatment, data centre, offshore energy, rail, and general industrial infrastructure. Contact us to discuss your project and the correct FRP specification for the climate your asset will operate in across its full design life.
Final confirmation of material suitability for any specific application — including thermal performance requirements and resin system selection for specific environmental exposures — remains the responsibility of the appointed project engineer. Reinforce Technology provides technical guidance and material recommendations based on information supplied to us, but specification sign-off should always sit with the qualified professional responsible for the design. We are happy to provide full technical data sheets and application-specific support to assist with that process.
References
Carbon Brief (2026) Met Office: A Review of the UK's Climate in 2025. Available at: https://www.carbonbrief.org/met-office-a-review-of-the-uks-climate-in-2025/ [Accessed: May 2026].
Climate Change Committee (2025) Progress in Adapting to Climate Change: 2025 Report to Parliament. Available at: https://www.theccc.org.uk/publication/progress-in-adapting-to-climate-change-2025/ [Accessed: May 2026].
IntechOpen (2022) 'Fibre-Reinforced Polymer (FRP) in Civil Engineering', in IntechOpen Engineering Series. Available at: https://www.intechopen.com/chapters/84203 [Accessed: May 2026]. [Steel thermal conductivity ~50 W/mK vs FRP 0.3–0.4 W/mK; steel thermal expansion ~12 µm/m/°C; steel yield strength reduction above 300°C].
Met Office (2025) Met Office Report Details Rising Likelihood of UK Hot Days. Available at: https://www.metoffice.gov.uk/about-us/news-and-media/media-centre/weather-and-climate-news/2025/met-office-report-details-rising-likelihood-of-uk-hot-days [Accessed: May 2026]. [Probability of exceeding 40°C in the UK accelerating; extreme heat events to become longer and more intense].
Met Office (2026) 2025 is Double-Record Breaker: UK's Warmest and Sunniest Year on Record. Available at: https://www.metoffice.gov.uk/about-us/news-and-media/media-centre/weather-and-climate-news/2026/2025-is-double-record-breaker-uks-warmest-and-sunniest-year-on-record [Accessed: May 2026]. [UK mean temperature 10.09°C; climate change made 2025 temperature ~260 times more likely; could now occur 1 in 3 years].
NACE International (2016) International Measures of Prevention, Application and Economics of Corrosion Technology (IMPACT). Houston, TX: NACE International. Available at: http://impact.nace.org/economic-impact.aspx [Accessed: May 2026]. [Elevated temperatures accelerate electrochemical corrosion reactions].
Royal Meteorological Society (2025) Annual Climate Stocktake Shows Weather Records and Extremes Now the Norm in UK Climate. Available at: https://www.rmets.org/news/annual-climate-stocktake-shows-weather-records-and-extremes-now-norm-uk-climate [Accessed: May 2026]. [UK warming at approximately 0.25°C per decade; last decade 1.24°C above 1961–1990 baseline].
ScienceDirect (2025) 'Sustainable composites for metal replacement: Environmental assessment and material selection of fiber-reinforced polymer across industries', ScienceDirect. doi: 10.1016/S2667-3789(25)00051-3 [Accessed: May 2026].
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