National Weather Service forecasts for Atlanta on September 22 point to a high near 91°F amid mostly sunny morning conditions before showers and thunderstorms develop in the afternoon, creating the tight spread across 86–91°F outcomes in the market. Key variables include the precise timing and coverage of convection, which could suppress the peak if storms arrive earlier, alongside model differences in boundary layer mixing and dew points near 70°F that influence realized maxima. Recent warmth has kept readings several degrees above late-September climatology, but the incoming frontal shift introduces measurable uncertainty in how far temperatures climb before clouds and precipitation intervene. Updated NWS guidance and afternoon model runs will provide the next clear signals on whether the high settles in the upper 80s or edges into the low 90s.