Recent National Weather Service and AccuWeather guidance places Houston’s May 18 maximum near the seasonal normal of 86–88 °F, with model consensus split between a partly cloudy regime that could reach the upper 80s and slightly higher humidity or lingering moisture that would cap readings at 84–87 °F. Traders therefore assign the highest probability (73 %) to the 86 °F or warmer bins, reflecting the narrow but non-negligible chance of a brief warm surge ahead of a weak frontal passage expected late in the day. Key differentiating variables include afternoon dew-point depression and boundary-layer mixing; drier air under clear skies favors the 88 °F-plus outcome, while increased cloud cover or onshore flow keeps temperatures in the mid-80s. Updated model runs this weekend will refine those thresholds before the market resolves.