Portugal has just endured its hottest May since records began, with average temperatures soaring 3.5°C above the 1981-2010 baseline. The heatwave, which settled over the Iberian Peninsula last week, pushed thermometers past 40°C in the Alentejo region, shattering previous monthly records by nearly 2°C. For context, this is not merely a statistical anomaly but a symptom of a climate system being systematically destabilised by human activity.
The Portuguese Institute for Sea and Atmosphere (IPMA) confirmed that the national average temperature for May 2024 reached 23.8°C, eclipsing the previous record set in 2020. More alarmingly, nighttime minimums remained above 20°C in many coastal areas, a phenomenon once rare outside July and August. This lack of overnight cooling is physiologically punishing for both ecosystems and human populations, particularly the elderly and those without access to air conditioning.
UK Met Office models now indicate that the same high-pressure system responsible for Portugal's scorcher is expected to migrate northwards, potentially dragging a plume of hot, dry air across the British Isles by mid-June. While such 'Iberian plumes' are not unprecedented, their increasing intensity is consistent with a warming climate. The Met Office has already issued an early warning for parts of southern England, where temperatures could reach the mid-30s Celsius, well above the June average of 20°C.
This event is part of a broader pattern. The global average temperature for May 2024 is on track to be the warmest on record, according to preliminary data from the Copernicus Climate Change Service. Ocean heat content also remains at record highs, providing the thermal energy that fuels these atmospheric extremes. Every fraction of a degree of warming amplifies the probability of such outlier events. What was once a 1-in-100-year extreme is now becoming a 1-in-10-year occurrence.
For policymakers, the message is clear: adaptation is no longer optional. Portugal's heatwave has already strained the energy grid, spiked hospital admissions for heatstroke, and dried out vegetation, raising the risk of wildfires. The UK should expect similar pressures. Investment in heat-resilient infrastructure, early warning systems, and public health interventions must accelerate. Renewable energy, particularly solar, also offers a pathway to reduce the fossil fuel emissions driving this crisis.
The physics is unambiguous. Greenhouse gases trap heat. More trapped heat means more extreme weather. And as the Portuguese data show, the extremes are arriving faster than many models predicted. The question is not whether we will face more record-shattering heat, but how well we can prepare for the inevitable.
