**Forecast models from the National Weather Service and other sources point to an overnight minimum near 55–56°F for Denver on September 18, 2026, as moderating cloud cover, humidity, and light winds limit radiative cooling.** Early-morning readings hovered in the low-to-mid 60s°F before the low, with afternoon highs expected near 82–89°F amid scattered thunderstorm chances. This places the daily minimum in a range where small shifts in timing of clouds, precipitation, or wind can easily move the outcome between the mid-50s and low-60s. Trader sentiment reflects this narrow band of uncertainty: the near-even split between “51°F or below” (~50%) and adjacent buckets around 58–59°F (~49.5%) captures model variability in how effectively the incoming moisture and surface winds suppress the typical clear-night drop. Historical September lows average near 49°F, but current conditions feature above-normal warmth and storm-related mixing that keep probabilities clustered in the upper 50s. Official resolution will rely on verified station data (e.g., Denver International Airport or NWS observations), with any late-evening showers or wind gusts serving as the key variables that could nudge the final minimum a degree or two in either direction.