**Persistent high pressure and a strong heat dome have kept Houston under mostly sunny, hot conditions on August 21, 2026, supporting the market’s heavy weighting toward 98–99 °F (63 % implied probability).** Official National Weather Service guidance and ensemble models consistently project a daily maximum near 98–100 °F at Houston-area airports, driven by southerly flow, dew points in the mid-70s, and minimal cloud cover that allows strong daytime heating. This pattern aligns with the ongoing heat wave and active Heat Advisory, which anticipates heat-index values near 106 °F. August climatology places normal highs around 94–97 °F, so current readings sit modestly above average, but the lack of afternoon convection or stronger sea-breeze mixing limits upside risk to the low 100s. Recent model runs show little spread, keeping the 100–101 °F bin at 23.5 % while lower bins (96–97 °F at 11 %) reflect only modest cooling scenarios. Traders are therefore anchoring probabilities to the latest NWS point forecasts and verifying observations rather than longer-term seasonal trends.