Current ensemble forecasts from the European Centre for Medium-Range Weather Forecasts and Météo-France show Paris overnight lows centered near 10–11 °C for May 21, with model spread producing comparable probabilities across the 9–13 °C range. A lingering maritime influence and weak upper-level trough over western Europe are limiting daytime heating while allowing radiational cooling under partly cloudy skies, keeping minimum temperatures close to the May climatological average of 9–10 °C at Paris-Le Bourget. Traders are therefore assigning nearly identical implied probabilities to adjacent temperature bins because small shifts in cloud cover, wind speed, or the timing of any frontal passage could easily move the actual low by 1–2 °C. Updated model runs expected over the next 48 hours will likely tighten the distribution ahead of the market’s resolution.