Recent National Weather Service guidance and model consensus point to a daily minimum in Denver around the mid-to-upper 60s on August 21, driven by scattered thunderstorms and elevated overnight humidity that limit radiative cooling under the Front Range’s typical August regime. With daytime highs forecast near 90–93 °F, the key variables separating the tightly bunched 62–69 °F bins are the timing of any clearing, boundary-layer wind speeds, and exact dew-point depression overnight—factors that produce only modest night-to-night variability this late in the season. Historical normals place the Aug 21 low near 57 °F, yet current moisture and storm activity have elevated the floor, explaining why sub-60 °F outcomes carry negligible market weight while the 68–69 °F bin leads. Updated NWS and NOAA model runs tonight will refine the final reading before official Denver observation closes the market.