UK weather: More heatwaves possible in second half of summer

Current meteorological trends suggest a potential for more unsettled weather to develop as summer progresses. However, forecasters caution that signals from various computer weather models are notably mixed, leading to a considerable degree of uncertainty in precise predictions. According to the latest sub-seasonal forecast provided by DTN, the BBC’s weather data supplier, there is an increasing probability that areas of low pressure will become more prominent over the coming weeks, especially across Scotland and Northern Ireland. The presence of low pressure systems typically brings more unstable atmospheric conditions, leading to an increase in cloud cover, stronger winds, and a higher chance of rainfall, including potentially heavy downpours or thunderstorms. This would offer a much-needed respite from the dryness in those northern regions.

Conversely, the influence of the Azores High, a semi-permanent large area of high pressure situated over the North Atlantic, is expected to remain a significant factor. This powerful anticyclone is renowned for its ability to block incoming weather fronts from reaching the UK, effectively maintaining drier and more settled conditions. While its proximity might temper the overall increase in wet weather, it is not expected to completely negate the chances of rain. For England and Wales, temperatures are most likely to persist above the seasonal average, raising the prospect of additional hot spells or even full-blown heatwaves extending into early August. This divergence in regional forecasts underscores the complex interplay of atmospheric systems influencing the UK’s summer climate.

The latest long-range forecast from the Met Office largely aligns with these predictions, hinting that "the influence of high pressure may wane somewhat" during the final week of July. Such a reduction in high-pressure dominance would pave the way for an increase in shower and thunderstorm activity. Initially, this unsettled weather is expected to affect the northern parts of the UK, gradually spreading southwards at various intervals. Looking ahead to the start of August, the Met Office forecast also anticipates a changeable period, but critically, it maintains the expectation of above-average temperatures and the continued possibility of further hot spells developing.

It is crucial to acknowledge that long-range forecasting, by its very nature, is fraught with uncertainty. The Earth’s chaotic atmosphere makes precise predictions increasingly difficult the further into the future one attempts to gaze. Forecasters primarily focus on identifying overarching trends and general patterns rather than offering day-by-day specifics. At present, these long-term trends for the latter half of the UK summer appear somewhat unclear, necessitating regular updates as new data becomes available. Weather models use complex algorithms and vast datasets to simulate atmospheric behaviour, but even the most advanced systems have limitations, especially when predicting events several weeks in advance. The difference between a "hot spell" and a full-blown "heatwave" often comes down to duration and intensity, which are harder to pinpoint with high confidence far in advance. Whatever personal plans individuals have for the remainder of the summer season, staying informed with the latest forecasts via reliable sources like the BBC Weather app will be essential for preparedness.

The summer of 2026 has already carved out a place in meteorological history as an extraordinary period of sustained heat. The record-breaking conditions began early with a late-spring heatwave that established a new temperature record for May. This was swiftly followed by another significant heatwave in June, and a third, exceptionally prolonged heatwave in July, which has persisted for two weeks in certain locations. By July 15th, the UK had already registered more days where temperatures exceeded 30°C than in the entirety of 1976. That year, 1976, is etched into collective memory for its iconic and exceptionally long-lasting heatwave, making the current summer’s performance particularly striking. Furthermore, this year marks an unprecedented meteorological event: it is the first on record where temperatures of 35°C or above have been reached in three distinct calendar months – May, June, and July – highlighting the unusual intensity and persistence of the heat.

A confluence of several interconnected factors has combined to drive the exceptional hot weather experienced across the UK this summer. Firstly, persistent areas of high pressure have been a dominant feature, allowing heat to accumulate steadily beneath them. High-pressure systems are characterised by sinking air, which suppresses cloud formation and leads to clear skies, maximising solar radiation reaching the ground. The descending air also warms through compression, further contributing to higher temperatures. Secondly, the severe lack of rainfall has resulted in widespread dry ground conditions. Dry land plays a critical role in amplifying heat because less of the sun’s incoming energy is expended in evaporating moisture from the soil and vegetation. Instead, a greater proportion of this solar energy is available to directly heat the ground surface and the overlying air, creating a positive feedback loop that intensifies temperatures.

Adding to these atmospheric conditions, sea-surface temperatures around the UK have been significantly higher than their normal seasonal averages, leading to what scientists term a "marine heatwave" that continues to affect our coastal waters. A marine heatwave occurs when ocean temperatures in a particular region remain unusually warm for an extended period. This phenomenon reduces the typical cooling effect that the sea usually provides to adjacent landmasses, especially during evening and overnight hours. Warmer seas can help to sustain higher temperatures over land, preventing the air from cooling down as much as it normally would, leading to warmer nights which can exacerbate the impacts of heatwaves on human health and infrastructure.

Underlying all these immediate meteorological drivers is the overarching influence of climate change. Scientists are increasingly confident that human-induced global warming is playing a fundamental role in making heatwaves not only more frequent but also more intense and longer-lasting across many parts of the world, including the UK. The Met Office, in its latest "State of the UK Climate report," has starkly warned that weather patterns previously classified as extreme are rapidly becoming the "new normal." The report emphasizes that the climate known throughout the 20th century is now a relic of the past, with the UK experiencing an approximate warming of 0.25°C per decade since the 1980s. This accelerating trend is directly linked to the accumulation of greenhouse gases in the atmosphere from human activities, trapping more heat and fundamentally altering global weather systems. The current summer serves as a powerful illustration of these long-term climatic shifts, underscoring the urgent need for both adaptation to a changing climate and mitigation efforts to reduce further warming.