France nuclear output curtailed as Garonne reaches 28 °C on 22 June

What happened: Record overnight temperatures above 25 °C raised river temperatures across southern France. EDF took Golfech-2 offline and reduced Nogent-sur-Seine output; additional reactors face derates later in the week. RTE data show total nuclear availability fell 2.8 GW below the seasonal norm by 24 June.

Evidence and data: Ember recorded 7 GW of French nuclear capacity offline during the July 2025 heat wave. IEA cooling-demand projections indicate European summer peak load will rise 18 % by 2030 under current climate trajectories. UK gas plants lost 2.5 GW of output in the same period, confirming thermal stress extends beyond nuclear.

Context and analysis: EDF’s February 2026 vulnerability assessment priced annual adaptation at €600 million, focused on cooling-system retrofits. The 13 % hydropower shortfall in the first five months of 2025 already tightened the supply margin, so further nuclear derates compound exposure rather than create it.

What comes next: RTE will publish weekly availability forecasts through 15 July; sustained river temperatures above 27 °C will trigger additional 500 MW derates at Bugey and Cruas.