Recent forecast guidance from the European Centre for Medium-Range Weather Forecasts and Global Forecast System models shows Helsinki’s May 18 maximum temperature centering on 18–20 °C, supported by southerly thermal advection of milder continental air and predominantly clear skies that promote strong daytime insolation. This consensus explains why trader-implied probabilities cluster tightly around 19 °C and 20 °C, with modest volume on 21 °C reflecting residual uncertainty in exact cloud timing and boundary-layer mixing. Historical May maxima in Helsinki average near 15 °C, so the current pattern represents a positive anomaly driven by a transient high-pressure ridge. Updated model runs and official Finnish Meteorological Institute observations over the next 48 hours will determine whether the peak settles at the lower or upper end of the favored range.