Recent ensemble forecasts from major meteorological centers show substantial spread in Paris's expected overnight minimum for May 20, with most runs clustering between 10–12 °C under a mild southwesterly flow. This narrow distribution of outcomes explains the tight clustering of market-implied odds around 11 °C and 12 °C. Scientific drivers include variable low-level moisture, the degree of cloud cover that modulates long-wave radiative cooling, and the timing of any weak frontal passage that could alter the nocturnal inversion. Historical May climatology places the average low near 10 °C, yet day-to-day fluctuations of 3–4 °C remain common this time of year. Updated model runs expected within the next 48 hours will likely tighten the range and shift probabilities among the leading outcomes.