**Trader sentiment for the lowest NYC temperature on August 21, 2026, centers on the 66–69°F range (62% combined implied probability), driven by late-summer atmospheric conditions and model consensus.** National Weather Service and AccuWeather guidance indicate overnight lows in the upper 60s to low 70s under partly cloudy skies, with radiational cooling limited by dew points near 65–70°F and the urban heat island effect. Long-range outlooks, including the Climate Prediction Center’s forecast for below-average temperatures late in the month and Almanac guidance for cooler air arriving around August 21–31, support a modest dip relative to mid-August normals of ~67–69°F. Recent model runs show limited spread absent strong cold advection or marine influence, keeping extreme bins below 3% probability while clustering most outcomes near the historical baseline adjusted for current patterns. Key resolution data will come from official Central Park or LaGuardia observations on the morning of August 21.