Recent ensemble forecasts from the Finnish Meteorological Institute and global models show Helsinki's August 17 maximum likely reaching 20–21°C under partly cloudy skies with moderate southwesterly flow. This tight clustering stems from subtle differences in predicted cloud timing and boundary-layer mixing over the Baltic Sea, which moderates peaks near the long-term August average of 19–20°C. Minor model spread in surface pressure and advection of slightly warmer air from the south creates the near-even split between those two outcomes, while probabilities drop sharply outside 19–22°C due to historical rarity of extremes this late in the season. Updated runs expected overnight will refine the exact daytime high before resolution.