Recent National Weather Service and model guidance indicate a frontal passage bringing cooler, moister air to Denver on September 29, with daytime highs near 67–69°F and overnight lows forecast in the upper 40s to mid-50s. This setup creates tight market-implied odds near 50% for a minimum of 47°F or below versus 49% for 66°F or higher because small differences in cloud cover, shower timing, and boundary-layer moisture will strongly influence nocturnal radiative cooling. Persistent low clouds or light rain suppress temperature drops by limiting longwave heat loss, while partial clearing under the post-frontal airmass allows greater cooling toward or below seasonal normals near 44°F. Updated model runs and surface observations over the next 48 hours will resolve these variables ahead of market resolution.