Current forecast models from agencies including the Japan Meteorological Agency indicate a maximum temperature of 21–22°C in Tokyo on October 5 under overcast skies and northerly flow, driving the market’s tight 44%–37% split between those outcomes. Persistent cloud cover reduces incoming solar radiation and limits daytime warming compared with clearer autumn conditions, while moderate winds enhance mixing and suppress peaks. Ensemble guidance shows limited spread around this range, with only modest upside potential if breaks in the clouds develop. Traders weigh these mesoscale factors against typical early-October baselines near 24°C, favoring the lower readings implied by the latest model runs ahead of final observations.