Forecast models from the National Weather Service and private sources show a 40% chance of afternoon showers and thunderstorms in Dallas on September 21, driven by an approaching upper-level disturbance and frontal boundary. This introduces uncertainty in solar heating and boundary-layer mixing, with guidance clustering between 92–97°F depending on storm timing, coverage, and resulting cloud cover. Southerly flow and elevated dew points near 65–70°F support strong instability but also favor scattered rather than widespread convection. Historical September highs in the mid-90s provide context, while the market’s tight distribution across the 92–97°F bins reflects this model spread and the resolution criteria tied to official Dallas-Fort Worth observations. Updated NWS briefings and afternoon model runs will likely refine the implied probabilities.