Latest Finnish Meteorological Institute and ECMWF ensemble forecasts project daytime maxima near 18°C in Helsinki under a high-pressure ridge and mild southerly flow advecting warmer continental air, producing above-average spring warmth relative to the 15–16°C climatological high. Trader consensus clusters around 17–19°C outcomes because model spreads of 2–3°C hinge on subtle differences in boundary-layer mixing, thin high-cloud timing, and solar insolation under mostly clear skies. These factors differentiate the closely matched probabilities, as reduced insolation or earlier frontal passage could cap peaks at 16°C while sustained clear conditions allow brief surges to 19°C before evening cooling. The final afternoon FMI update will narrow resolution based on official 24-hour maximum readings at Helsinki-Vantaa.