Recent National Weather Service and model guidance shows a cool, moist northeasterly flow over the Northeast following Sunday’s rain, limiting daytime heating in New York City on September 21. Forecast highs cluster in the upper 60s to low 70s, with persistent cloud cover and a 20–40% chance of light showers keeping maximum temperatures near the 68–71°F range that dominates trader probabilities. Differences between the closely matched 68–69°F and 70–71°F bins hinge on the precise timing of any breaks in cloudiness and boundary-layer mixing under the stable post-frontal airmass; stronger subsidence or earlier clearing could briefly push readings into the low 70s, while lingering stratus would cap them below 70°F. Updated model runs and afternoon observations will refine these thresholds ahead of market resolution.