The Beznau nuclear plant will be shut down today, as the Aare river has reached the 25-degree threshold.
The plant has been running at half capacity since Tuesday. The shutdown is not to protect the plant itself but the river's ecosystem, which is already under heat stress.
Operator Axpo says national supply remains secured through imports while Beznau is offline.
The same plant was switched off for around a week last July for exactly the same reason.
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