Traders see the lowest temperature in Paris on July 23 clustered near 15–17 °C because short-range ensemble forecasts from Météo-France and ECMWF show overnight radiative cooling under partly cloudy skies with light winds yielding minimums in that narrow band. Clearer intervals allow greater surface heat loss and could push readings toward 14–15 °C, while increased low-level moisture or a modest nocturnal breeze limits cooling and favors 16–17 °C. These thresholds sit close to the July climatological average low of roughly 15–16 °C at Paris-Montsouris, so modest shifts in model guidance on cloud cover or boundary-layer mixing keep the three central bins nearly tied. Updated 00Z and 12Z runs over the next 48 hours, plus official station verification, will resolve the spread.