Recent Finnish Meteorological Institute model guidance points to a daytime maximum near 16–17 °C in Helsinki on May 17, driven by strong solar insolation under a weakening high-pressure ridge and light southerly winds advecting mild continental air. Ensemble runs from GFS and ECMWF show only modest differences in boundary-layer mixing and thin afternoon cloud timing, which explains why trader-implied probabilities sit almost evenly between the 16 °C and 17 °C brackets. Mid-May climatology for the Helsinki-Vantaa station averages 14–15 °C, so current conditions sit slightly above normal; any increase in low-level stratus or earlier wind shift could cap the peak at 16 °C, while clearer skies would allow a brief 17 °C reading before evening cooling sets in.