Forecast uncertainty in short-range numerical weather prediction models is the main driver behind the tight clustering of trader probabilities around 20–23°C for Moscow’s July 23 daily maximum. Ensemble spreads show modest variability in daytime heating tied to subtle differences in cloud cover, boundary-layer mixing, and weak cold-air advection ahead of a passing trough. Historical July climatology places the long-term average high near 23°C, yet current guidance from multiple centers indicates slightly suppressed values around 20–22°C due to increased cloudiness and lighter winds. Resolution hinges on the official Moscow station reading, where even a 1°C shift from model bias or local microclimate effects can separate the leading outcomes. Updated runs ahead of the 48-hour window will likely tighten or shift these probabilities as new observational data arrives.