Recent National Weather Service forecasts and ensemble model runs indicate Atlanta highs on September 20 will likely peak in the upper 80s to low 90s as increased moisture and scattered afternoon thunderstorms limit full insolation compared with the hotter, sunnier conditions of September 18–19. Official point forecasts center near 90–91°F, with heat indices potentially reaching the upper 90s before any storms develop, while climatological normals for the date sit around 82°F. This consensus, reinforced by consistent guidance across regional models, underpins the market’s leading 90–91°F bin at 40.5% implied probability, with secondary support for 88–89°F reflecting residual uncertainty in storm timing and coverage that could shave a degree or two from the daily maximum.