The Iberian Peninsula has shattered its May temperature record, with Portugal registering 36.9°C in the central Alentejo region on Thursday. This event, occurring two weeks before the official start of meteorological summer, has triggered the activation of the UK's Heatwave Plan for England. The Met Office has issued a Level 2 alert, indicating a 60 per cent probability of heatwave conditions in parts of southern and central England over the next 72 hours.
The record in Portugal, confirmed by the Portuguese Institute for Sea and Atmosphere (IPMA), represents a 1.2°C increase over the previous May high set in 2019. Climatologists attribute this anomalous warmth to a persistent blocking pattern over the North Atlantic, stalling a high-pressure system that is drawing hot, dry air from North Africa. This pattern, colloquially termed an 'omega block' for its shape in atmospheric charts, is becoming more frequent under a warming climate.
Dr. Sofia Ribeiro, a climatologist at the University of Lisbon, stated: "What we are observing is not an outlier but a trend. The probability of exceeding previous May temperature records has increased by a factor of five since the pre-industrial era. This is consistent with the long-term warming signal."
The UK Heatwave Plan, revised annually by Public Health England, is a strategic framework developed after the 2003 European heatwave that caused over 2,000 excess deaths in the UK alone. The Level 2 alert is a pre-emptive measure, urging healthcare providers to check on vulnerable individuals, particularly the elderly and those with respiratory conditions. Local authorities are advised to open cooling centres and ensure adequate hydration in care homes.
Professor Sir Ian Boyd, former chief scientific adviser at the Department for Environment, Food and Rural Affairs, warned: "The frequency of heatwaves is accelerating. Our infrastructure, from housing stock designed for cold winters to transport networks with heat-sensitive rails, is not adapted to this new reality. Each heat event is a stress test we are failing."
Data from the UK Health Security Agency indicates that the 2022 heatwave, when temperatures exceeded 40°C for the first time, caused 3,000 excess deaths. With the current event, early modelling suggests a 15 per cent increase in ambulance callouts for heat-related illnesses if temperatures reach 30°C in London by Monday.
Energy systems also face strain. National Grid has issued a portfolio of flexibility notices, requesting that power generators delay maintenance to ensure capacity. Solar generation, ironically at peak output, is expected to cover the increased demand for air conditioning, but grid operators remain vigilant for potential imbalances.
Ecologically, the early heat compounds existing drought conditions. The Environment Agency reports that 19 of 24 water resource zones in southern England are now under 'serious' water stress. River flows in the Thames catchment are at 60 per cent of the long-term average for this time of year. Farmers are advised to postpone planting or risk crop failure due to soil moisture deficits.
Looking ahead, the Met Office's seasonal forecast indicates a 40 per cent probability of a hotter-than-average summer, with the climate model showing a clear warming trend since 2000. Dr. Mark McCarthy, head of the Met Office's climate attribution team, stated: "The question shifts from 'is this climate change?' to 'how much worse can we expect?' For every degree of global warming, the intensity of heatwaves increases by about 2-3°C in mid-latitudes due to land-atmosphere feedbacks."
The activation of the Heatwave Plan is not a cause for panic but a measured response. However, each activation underscores the shrinking gap between current resilience and the escalating demands of a changing planet. The record in Portugal is a snapshot of a larger film: the Earth's energy imbalance, now at 0.9 W/m² above the 2000 baseline, is manifesting in discrete extreme events. These are not outliers; they are the distribution shifting. Our infrastructure, our agricultural systems, and our health services must adapt at a pace that matches the physical reality of our warming world.
