The sun might be the toughest opponent athletes competing at the Paris Games will face.

Climate change and the impact of El Nino have forecasters predicting 2024 will be the planet’s hottest summer on record.

With that in mind, one “green” choice by the 2024 Olympic organizing committee — which is aiming to stage the most sustainable Games ever — has struck a nerve with delegations concerned about the heat: the decision not to install air conditioning in the athletes village. Instead, an eco-friendly underground cooling system that draws water from the River Seine will be used.