**High atmospheric moisture and elevated dew points in the low 70s°F are the dominant factors limiting overnight radiative cooling, anchoring trader consensus on a lowest temperature of 70–71°F for New York City on August 20, 2026 (45.5% implied probability).** Persistent southerly flow under the Bermuda High has maintained a tropical airmass across the Northeast, with recent observations showing dew points supporting minimal temperature drops despite clear or partly cloudy skies. Warmer-than-average August baselines—driven in part by the strengthening El Niño pattern—further reduce the likelihood of stronger cooling, while model guidance from the National Weather Service and ensembles points to overnight lows clustered in the upper 60s to low 70s. Lower-probability outcomes below 68°F would require an unexpected frontal passage or sharp drop in humidity, scenarios not currently favored in short-range forecasts. The tight clustering around 70–73°F (combined ~85.5%) reflects this stable humid regime, with traders assigning only modest odds to modest variations from model runs or micro-scale cloud effects.