**Trader consensus on the Polymarket for Tokyo’s October 5 highest temperature centers on 21–22 °C because multiple forecast models show a modest autumn high under persistent cloud cover and northerly flow.** Official guidance and ensemble runs from sources such as the Japan Meteorological Agency and global models indicate daytime maxima near 21 °C, with limited solar heating from overcast skies and breezy northwest winds keeping readings from rising further. Recent observations on October 4 reached only 22–23 °C under similar conditions, reinforcing the expectation of modest warming the following day. The 23 °C outcome carries secondary weight in case any clearing occurs, while probabilities for 20 °C or below remain low given the current thermal profile. Updated model runs and observational data later on October 4 will refine these market-implied odds ahead of resolution.