Are ‘heat spikes’ becoming more common?
Are ‘Heat Spikes’ Becoming More Common?
Are heat spikes becoming more common – Throughout May, much of the UK has felt the impact of an unusual heatwave, with temperatures soaring to levels not typically seen at this time of year. This week, a record-breaking 35.1°C was recorded, marking an atypical spike in heat during May. In the days leading up to this extreme weather, temperature rises were dramatic, with some areas experiencing a 10°C increase in just two days. Such a rapid escalation contrasts with historical norms, where temperatures usually climbed gradually by a degree or two daily.
Experts have observed that these sudden temperature jumps—referred to as ‘heat spikes’—are occurring more frequently. Ed Hawkins, a climate scientist at the University of Reading, noted to the BBC that “Today’s heat events are emerging earlier, intensifying faster and occurring across a much warmer background climate.” While Dr. Ségolène Berthou of the Met Office acknowledged that “We can’t explicitly say that extreme heat temperatures spike faster now than they did in the past,” she emphasized that other climate factors are contributing to the changing pattern.
UK Climate Trends and Heatwave Thresholds
The Met Office’s State of the Climate 2024 report highlights a concerning shift in the UK’s temperature dynamics. It reveals that the hottest days are warming at roughly twice the rate of typical days. This means that the number of days exceeding 5°C above the average has more than doubled since the 1961–1990 period, while days surpassing 10°C above the average have quadrupled. As Dr. Berthou explained, “Extreme temperatures are increasing faster than average temperatures,” underscoring the accelerated pace of heat events.
Comparing the 1991–2020 climate period with the 1961–1990 baseline, summer daytime highs have risen by approximately 1.5°C. This warming trend is evident even in regions where heatwaves were previously less common. Notably, the UK hit a summer high of 40.3°C in July 2022, a temperature that was once rare but is now more frequently expected. Met Office research indicates that the likelihood of surpassing 40°C has increased by over 20 times compared to the 1960s.
Contributing Factors to Intense Heat Events
Temperature surges are not solely dependent on how warm the air begins, but also on the condition of the land and atmosphere. Dry ground absorbs heat more efficiently than moist soil because less energy is used for evaporation. This explains why the UK is witnessing more frequent droughts, which can deplete reservoirs and intensify heat conditions. For instance, a notable drought in Derbyshire during August 2025 highlighted the growing risk of prolonged dry spells.
High-pressure systems, often termed blocking highs or heatdomes, play a critical role in these heat spikes. When such systems linger, they create descending air that dries the atmosphere, similar to squeezing a sponge. The compression of air within these systems further amplifies warming. Although the frequency of blocking highs may not have changed, their impact has intensified, delivering hotter and drier conditions than in previous decades. Professor Sarah Perkins-Kirkpatrick from the Australian National University remarked, “The dice are loaded for it to be hotter more quickly…as soon as high pressure systems move over, bang, the temperature goes up.”
Wind direction also influences the UK’s heat patterns. South or south-easterly winds are linked to the most intense heat, as they transport warmer air from southern Europe and North Africa. Europe’s warming, which occurs at about twice the global average, especially in southern regions where extreme heat events are most pronounced, provides a hotter source of air. This means that a more frequent southerly airflow can rapidly bring elevated temperatures to the UK. Such wind shifts can happen swiftly, helping to explain why heatwaves can develop within days of average temperatures.
Marine Heatwaves and Their Impact on Land Temperatures
Sea surface temperatures around the UK may also be a key player in these heat spikes. Dr. Berthou pointed out that “We are seeing more frequent and persistent marine heatwaves in the seas around the UK,” which can influence land temperatures. In June 2023, for example, London experienced a rapid temperature rise from 23°C on June 8 to 31°C by June 10. This coincided with UK sea surface temperatures that were 3–5°C above the historical average, demonstrating a direct link between oceanic warming and land-based heat extremes.
The combination of these factors—warmer baseline climates, drier land, and enhanced high-pressure systems—creates a perfect storm for heat spikes. While the primary cause of these events may be related to broader climate changes, local weather patterns and atmospheric conditions also contribute. The Met Office projects that seasonal drying is occurring earlier than before, particularly in southern and eastern England, increasing the frequency of droughts. These changes are already evident in the way that heatwaves can develop within days, rather than weeks, of mild weather.
As the UK continues to experience warmer summers and more rapid temperature fluctuations, the implications for agriculture, energy demand, and public health are significant. The accelerating pace of heat events suggests that the region is becoming more vulnerable to extreme weather, even if the exact mechanisms remain complex. By understanding the interplay between these factors, scientists hope to better predict and prepare for the future of heat in the UK.
Climate scientists are confident that these trends will persist. The shift from gradual temperature increases to sudden spikes reflects a broader transformation in weather patterns driven by global warming. With each passing year, the UK’s climate is reshaping itself, and the signs are clear: heat events are not only arriving earlier but also hitting harder than they did in the past. This means that the UK may soon face a new normal of more frequent and intense heatwaves, requiring updated strategies for adaptation and resilience.