Current ensemble forecasts from the European Centre for Medium-Range Weather Forecasts and Global Forecast System show substantial spread in overnight minimum temperatures for Paris on May 21, with solutions clustering between roughly 7°C and 17°C. This uncertainty arises from competing influences: a lingering cool anomaly across western Europe that favors radiative cooling under clear skies and light winds, versus potential warm advection from the Atlantic if a maritime ridge strengthens. Mid-May climatological averages place typical lows near 9–11°C, so the market’s near-equal implied probabilities on the coldest and warmest buckets reflect genuine model disagreement rather than a single dominant signal. Fresh runs expected in the next 24–48 hours will likely tighten the range ahead of the May 21 resolution.