Latest forecast models from the Finnish Meteorological Institute and European Centre for Medium-Range Weather Forecasts indicate a maximum temperature of 18°C for Helsinki on May 21, driven by a stable high-pressure system bringing clear skies and moderate northwesterly flow. This aligns with climatological norms for late May in southern Finland, where daily highs typically range 15–20°C under similar synoptic conditions. While ensemble runs show minimal spread around this value, small deviations could occur if afternoon cloud cover develops or localized sea-breeze effects intensify, potentially shifting the peak by 1–2°C. Traders have positioned overwhelmingly on 18°C as the resolution threshold because official observations from Helsinki-Vantaa airport, the market’s reference station, are expected to confirm this exact maximum before midnight.