Recent atmospheric conditions over the western Pacific have favored a modest warming trend into mid-May, with southerly flow and reduced cloud cover supporting daytime maxima near or slightly above seasonal norms of 23–25 °C for Tokyo. Ensemble forecasts from global models show a narrow spread for 17 May, with most solutions clustering between 28 °C and 31 °C depending on the exact timing of any frontal passage and the strength of insolation. The closely matched market prices for 29 °C and 30 °C-plus reflect this tight uncertainty band, where small differences in boundary-layer moisture or wind direction could shift the daily peak across the 30 °C threshold. Updated runs from the Japan Meteorological Agency and ECMWF in the next 24–48 hours will provide the clearest signal ahead of the event.