Recent forecasts from meteorological models indicate overnight lows in Helsinki around 10–13°C on August 21, driven by a cool, moist air mass with variable cloud cover and light southerly winds limiting radiative cooling. Historical averages place the typical minimum near 13°C, but recent cooler patterns and possible showers have shifted trader focus toward 11–12°C outcomes. Ensemble model spreads create tight probabilities across 9–13°C, reflecting uncertainty in exact cloud timing and wind speeds that influence how much the temperature falls after sunset. Official guidance from sources like the Finnish Meteorological Institute and ECMWF runs will refine this as the night progresses, with any clearing skies potentially allowing dips toward the lower end of the range.