As the UK endures an extended heatwave, many regions have experienced an unbroken stretch of sweltering conditions that has lasted nearly two weeks. Southern England, in particular, has recorded 13 consecutive days surpassing the established heatwave criteria, with Merryfield in Somerset reaching a peak temperature of 30.6°C (87.1°F) on Thursday. This marks the UK’s longest run of temperatures at or above 30°C since 2006, with Bournemouth and Heathrow also reporting high temperatures over 26°C and 28°C, respectively. While a slight cooling trend is anticipated this weekend, certain areas may yet experience additional days of extreme heat.
The Origins of the Current Heatwave
The persistence of this heatwave can be attributed to a confluence of climatic factors. The UK is currently witnessing an average temperature increase of 1.33°C compared to the period from 1961 to 1990. Notably, the hottest days have warmed at a striking rate—approximately 4.5°C in Greater London, as reported by the Met Office.
This summer’s atmospheric conditions have been particularly favourable for the sustenance of heat. The jet stream has shifted far north of the UK, allowing a high-pressure system to dominate and facilitate the inflow of warm air from southern regions. The immobility of this high-pressure system has resulted in the formation of a “heat dome,” characterised by descending air that compresses and heats as it descends. This dynamic not only eliminates cloud formation but also allows for intensified solar heating of the ground.
Distinguishing Features of This Year’s Heatwave
2023 is shaping up to be a landmark year for weather extremes in the UK, having already shattered monthly temperature records for both May and June by significant margins—over two degrees. This current heatwave represents the third of the year, with 12 days exceeding 30°C across various parts of England and Wales. In contrast, the same period last year also saw its third heatwave but did not reach these extreme levels.
While parts of Scotland and Northern Ireland have also felt the heat, the intensity has been markedly less severe and shorter-lived. Comparisons are being drawn with the legendary summer of 1976, which still holds the record for the longest heatwave. However, this year has experienced more days of extreme heat, with some areas in southern England, such as Wisley in Surrey, recorded as rainless for 30 days.
The intensity of this year’s heat is evident, with six days exceeding 35°C recorded so far—an unprecedented occurrence for three consecutive months (May, June, and July).
Shifting Heatwave Patterns
The Met Office has indicated that heatwaves in the UK are becoming increasingly frequent, prolonged, and intense. Their latest State of the UK Climate report notes a fourfold increase in the number of days exceeding 30°C in regions like Greater London. Notably, heatwaves are no longer confined to the traditional summer months; a significant autumn heatwave in September 2023 saw temperatures soar above 30°C for seven consecutive days.
This year’s earliest heatwave emerged in late May, which not only set the record for the highest May temperature but also introduced the UK’s first tropical night of 2023, with an overnight minimum temperature of 21.4°C.
Forecast and Future Conditions
As we move into the weekend, meteorological forecasts suggest a shift to northerly winds, resulting in a modest decrease in temperatures for many regions. Scotland, Northern Ireland, and parts of north-east England will experience increased cloud cover and cooler temperatures in the low 20s. Meanwhile, southern England and Wales are likely to remain sunny and warm, with temperatures ranging between 24°C and 27°C—although some locations may still reach 28°C or 29°C.
Looking ahead, the remainder of July is expected to see high pressure maintaining generally dry and warm conditions, albeit with temperatures not matching the extremes of recent days. Late July may bring some showers, particularly in northern areas. As August approaches, weather models suggest a return to more variable conditions, although above-average temperatures are likely to persist.
Why it Matters
The ongoing heatwave not only highlights the immediate challenges posed by extreme weather in the UK but also serves as a stark reminder of the broader implications of climate change. As heatwaves become more frequent and intense, the pressure on infrastructure, public health, and natural resources intensifies. The data underlines the urgent need for adaptive strategies to mitigate the impacts of such climatic extremes, emphasising the critical importance of climate resilience in policy and urban planning.
