Extreme heat and drought have pushed major European rivers to exceptionally low levels, forcing nuclear shutdowns and output cuts from Romania to France and highlighting a growing climate-resilience challenge for Europe’s electricity system.
Europe’s prolonged heat and drought are putting the continent’s power system under mounting pressure, constraining nuclear generation just as high temperatures increase electricity demand for cooling.
The most acute problems are unfolding along the Danube, where exceptionally low water levels have disrupted nuclear generation in Romania and Hungary. Romania began a controlled shutdown of the second reactor at its Cernavodă nuclear plant after its first reactor was taken offline in late July, temporarily removing a facility that normally supplies roughly 20% of the country’s electricity. The operator said the shutdown posed no nuclear-safety risk.
The move came despite engineering interventions intended to redirect more Danube water toward the plant’s cooling system.
Hungary has also come close to a complete nuclear shutdown. Its Paks plant, which normally supplies roughly one-third of the country’s electricity, was reduced to a fraction of its 2,000-megawatt capacity as Danube levels fell. The government has announced measures intended to raise water levels near the facility and keep it operating.
Together, the disruptions underscore a challenge facing countries that continue to rely heavily on nuclear power: maintaining reliable generation as hotter temperatures and lower river flows place increasing pressure on water-dependent infrastructure.
France Faces Heat-Related Nuclear Curbs
The pressure extends westward to France, home to Europe’s largest nuclear fleet.
EDF expected extreme heat to remove around 15% of France’s nuclear capacity on Friday, with approximately 9.4 gigawatts curtailed across nine reactors and six reactors going fully offline, according to Reuters. Temperatures approaching 40°C have raised river temperatures, triggering environmental restrictions on the discharge of heated cooling water.
These curtailments are not indications of reactor failure. Nuclear plants require substantial cooling, and France limits how much heated water plants can release into rivers to protect aquatic ecosystems. When river temperatures become unusually high, operators can therefore be required to reduce generation even when reactors remain technically capable of operating.
The reductions have nevertheless affected regional power markets. French day-ahead electricity prices for Friday rose to €154.50 per megawatt-hour, even as France remained a net electricity exporter.
At the same time, weak wind conditions have reduced generation elsewhere in Europe. German wind output was expected to fall sharply below seasonal averages earlier this week, contributing alongside French nuclear curtailments to higher electricity prices.
That combination illustrates why Europe’s current energy stress cannot be viewed solely as a nuclear-power problem.
Drought Becomes an Energy-Security Issue
The nuclear disruptions are part of a broader drought affecting large parts of Europe.
The European Commission’s Joint Research Centre reported this week that exceptionally low river flows have been recorded across major waterways including the Danube, Rhine, Loire and Po, with warmer and drier conditions expected to persist in some regions into September.
The consequences extend well beyond nuclear plants. Low water levels can reduce hydropower generation, restrict inland shipping and affect agriculture and industrial activity. Extreme heat can simultaneously increase wildfire risk and push electricity demand higher.
Europe is therefore confronting a more complex energy-security challenge in which several parts of the power system can come under pressure at the same time.
Nuclear plants can face cooling-water constraints. Drought can weaken hydropower output. Calm weather can reduce wind generation. Extreme temperatures can strain grids and thermal power stations while increasing electricity consumption.
The result is a growing premium on diversification and resilience across the electricity system.
Nuclear Remains Central to Europe’s Energy Mix
The current disruptions do not fundamentally alter nuclear power’s importance to Europe.
Nuclear plants generated 23.2% of EU electricity in 2025, according to Eurostat, broadly unchanged from the previous year. France remains particularly dependent on the technology, with nuclear supplying roughly two-thirds of its electricity.
At the same time, renewable generation has expanded rapidly, leaving Europe increasingly reliant on a power system in which nuclear, wind, solar, hydropower, storage and cross-border interconnections complement one another.
This summer demonstrates both the strength and the vulnerability of that model. When one source is constrained, others can compensate. But increasingly extreme weather can also affect several technologies at once.
For European governments, that shifts the policy challenge from simply expanding clean-energy capacity to ensuring that the broader system can continue operating reliably under more demanding conditions.
Designing Power Systems for a Changing Climate
Cooling-water constraints at nuclear plants are not new. France has curtailed nuclear generation during previous heatwaves, including in 2022, when authorities temporarily adjusted environmental rules governing thermal discharges from several plants to maintain electricity production.
But increasingly severe heat and drought are raising the importance of climate resilience in decisions about existing and future energy infrastructure.
For nuclear operators, adaptation options can include cooling towers, closed or hybrid cooling systems, alternative water supplies and different approaches to plant siting. Existing facilities can be more difficult and expensive to retrofit, making those considerations particularly important when governments evaluate reactors expected to operate for decades.
The same challenge applies across the electricity system. Hydropower facilities, transmission networks, renewable generation, storage and water infrastructure will all need to function under potentially more volatile climatic conditions.
Europe’s current experience therefore does not demonstrate that nuclear power is incompatible with a warming world. Rather, it points to a broader reality confronting governments pursuing both decarbonization and energy security: low-carbon infrastructure must itself be resilient to climate extremes.
As electricity demand grows through transportation, industry, cooling and data centers, that requirement will become increasingly important.
The strategic question for Europe is no longer simply how much clean generating capacity it can build. It is whether the continent can develop an electricity system capable of delivering reliable power when heat, drought, low wind and other stresses occur at the same time.
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