**Forecast consensus from National Weather Service and major models points to an overnight low in the upper 70s°F for Houston on September 17, 2026, driven by persistent warm, humid air under high pressure with limited radiational cooling.** East-southeast winds of 5–10 mph, dew points near 74–77°F, and afternoon thunderstorm chances (40–50%) will maintain elevated minimum temperatures, consistent with recent September patterns where actual lows have run several degrees above the 1991–2020 climatological average of ~72°F. Model agreement is relatively tight on this range, though subtle differences in cloud cover or outflow boundaries from daytime convection could shift the exact low by 2–4°F. The closely matched market-implied odds on the extremes (73°F or below versus 92°F or higher) reflect trader hedging around residual uncertainty in mesoscale features and the narrow historical window for cooler September nights, while the spread across mid-70s to low-80s bins captures the typical forecast error range for a single-night minimum in this subtropical climate. Updated NWS guidance and evening model runs will provide the next key data points before resolution.