Current ensemble forecasts from major global models show significant spread for Paris overnight minimum temperatures on May 20, with guidance clustering between 8°C and 14°C depending on the strength and position of an approaching high-pressure ridge. This range arises from subtle differences in modeled cloud cover, radiational cooling rates, and weak southerly flow that could either moderate or enhance nighttime temperature drops. Historically, mid-May lows in the region average near 10°C, but the current setup lacks strong steering patterns that would lock in a narrower outcome. Traders price the 11°C and 16°C-or-higher buckets near 46% each because fresh model runs through the weekend remain sensitive to small shifts in boundary-layer moisture. Updated 00Z and 12Z cycles from ECMWF and GFS, expected over the next 48 hours, will likely tighten probabilities as the event moves inside the 72-hour window.