Latest National Weather Service model runs point to a high near 63°F at Chicago’s official O’Hare station on May 22, driven by a lingering cool air mass and northerly flow behind a recent frontal passage. Ensemble guidance shows modest warming potential from daytime mixing and partial sunshine, yet persistent cloud cover and a breeze could cap readings in the low-to-mid 60s. This places the most likely outcome near the 64–66°F range, consistent with the market’s closely bunched probabilities around those bins. Historical climatology for late May shows a normal high of roughly 73°F, underscoring how this cooler pattern deviates from seasonal averages and leaves room for modest forecast adjustments before resolution.