Europe's heat is now a supply event: 38.1C in the UK, reactors off along the Danube

Britain's Met Office said on August 15 that Kew Gardens in west London hit a provisional 38.1C on the 13th, beating the year's previous high of 38C set on June 28 ^[1]. On the same day, Romania began disconnecting the last operating reactor at Cernavoda from the grid because flow in the Danube had fallen to roughly 1,350 cubic metres per second ^[10]. One of those is a temperature record; the other is a capacity loss that utilities and heavy electricity users now have to budget for.

The size of the loss is the point. Cernavoda's two 700MW units ^[11] amount to 1,400MW of nameplate capacity ^[1], and the plant had been supplying about 20% of Romania's total output before halting completely for the first time since 2003 ^[11]. Hungary's exposure is proportionally larger: Paks, its only nuclear plant, provides about 40% of national electricity ^[13], and its four reactors were shut in sequence from July 29 until the site stopped entirely on August 2, the first full halt in 44 years of operation ^[14]. According to Seoul Economic Daily, these were cooling-water shutdowns caused by record low Danube levels, not equipment failures ^[9].

The substitutes are thin. Romania declared an energy state of emergency for August, raised output at a 330MW lignite plant, expanded hydro and wind, and cited about 4,000MW of cross-border import capacity ^[12]. The lignite unit covers roughly a quarter of the nuclear nameplate that went offline ^[2], and import capacity is nominally about 2.9 times it ^[3], but that headroom competes with neighbours under the same weather. Semafor reported that a fifth of France's nuclear capacity was offline during the same heatwave ^[17], with parts of Germany and France forecast above 38C at the peak ^[18].

Persistence, not the single peak, is what makes this a planning item. The UK logged 35 days at or above 30C this year, an all-time high ^[4], and daily highs cleared 35C in four consecutive months from May through August for the first time on record ^[3]. The average temperature from June 1 to August 10 was 16.48C, putting Britain on course for its hottest summer since records began in 1884, 0.36C ^[5] above last year's record of 16.12C ^[5]. This was the fifth heatwave of the summer ^[8]. France's ran into a 17th day, with 39C in Bordeaux and 37C in Paris ^[7]. About three-quarters of England and all of Wales were in drought ^[6], and EFFIS assessed cumulative EU wildfire risk since the start of the year at the highest level on record ^[21].

Swiss Re, in a report cited by Semafor, warned that rising temperatures on the continent will strain water and energy systems, damage infrastructure, cut agricultural productivity and lower labour productivity ^[19]. That is a demand shock and a supply shock arriving in the same weeks. Roman restaurants and bars reported falling sales last month ^[20].

Watch whether the river recovery holds. Rainfall in the Austrian basin lifted the upper Danube early this month and Paks restarted its turbines on the 10th, though full output will take longer ^[15]. Bulgaria's Kozloduy kept running on the lower Danube while dredging and monitoring conditions ^[16]. Romania's emergency declaration covers the month of August ^[12], so the next data point is what its balance looks like when the declaration lapses. For anyone contracting power or siting load in southeast Europe, the operative question is whether river-cooled baseload can still be priced as firm capacity in July and August.