Current forecasts from models like GFS and local agencies indicate Helsinki's minimum temperature on September 18 will likely fall between 10–13°C, driven by persistent southwesterly flow advecting mild maritime air, extensive cloud cover limiting radiational cooling, and scattered rain enhancing boundary-layer mixing. Trader sentiment reflects tight clustering around these values because small shifts in frontal timing or wind speeds could push the overnight low toward 9°C or hold it near 14°C, while the 33.5% odds on 5°C or below and 15°C or higher capture tail risks from model divergence or unexpected clear-sky periods. Historical September averages near 8–13°C provide context but carry limited weight given the active synoptic pattern.