Forecast models from sources including the Met Office, GFS, and European centers indicate London highs on September 25 will likely reach 23–27 °C, driven by a stable high-pressure pattern with southerly or light variable winds promoting daytime warming under partly cloudy skies and minimal precipitation. Recent observations show persistent above-average temperatures for late September, with afternoon peaks near 24–26 °C amid low humidity and clear spells. Key variables differentiating outcomes include cloud-cover timing, which can suppress maxima by 2–3 °C, and any late wind shift to northwesterly flow that enhances mixing. Ensemble spreads and historical September variability support the market’s tight clustering around 24–28 °C, with lower probabilities assigned to extremes outside this range. Updated model runs and official Met Office briefings over the next 48 hours will refine these projections ahead of resolution.