About this Market

Recent Met Office and ensemble forecasts indicate a maximum temperature of 19–22°C in London on September 20, driven by building high pressure and northwesterly flow that limits warming while allowing sunny intervals and light winds. Model consensus points to afternoon peaks near 20–21°C, with minor spread arising from variable cloud cover and exact steering patterns. The market’s heavy weighting toward 20°C and 21°C reflects this narrow range and the resolution criteria based on official observations, while lower probabilities for 22°C or above acknowledge historical September variability and potential for modest cooling. Updated model runs and real-time synoptic data over the next 48 hours will further constrain the outcome.