Traders are closely split between 18°C and 19°C for Paris’s daily minimum on August 10 because ensemble forecasts from ECMWF and GFS show nighttime radiative cooling under mostly clear skies yielding lows near 18–20°C, with modest model spread around the exact value. A lingering warm air mass from the current European heatwave supports the upper end of that range, while potential Atlantic moisture advection or increased low-level cloud cover could enhance downward longwave radiation and nudge the minimum a degree lower. Wind speeds remaining light overnight and surface humidity levels around 60–70% limit further cooling below 17°C. With resolution only two days away, the next model runs and Météo-France updates on boundary-layer mixing will likely tighten the market-implied odds.