National Weather Service forecasts for Atlanta on September 20 project a high near 91°F under mostly sunny skies with light easterly winds and only a slight afternoon thunderstorm chance, supporting the market's tight clustering between 88–91°F outcomes. Afternoon convection timing and coverage remain the key variables, as scattered storms could reduce insolation and cap the maximum before peak heating, while clearer conditions would favor readings at the upper end of that range. High humidity and unseasonably warm regional patterns sustain elevated baseline temperatures, but ensemble model spread on boundary-layer mixing and any early cloud build-up creates the narrow probability gap between the two leading bins. Updated model runs and NWS briefings through the day will likely refine trader positioning ahead of resolution.