Trader consensus on Polymarket heavily favors Chicago's highest temperature on April 20 at 55°F or below (74.5% implied probability), aligned with National Weather Service guidance and ensemble forecast models like GFS and ECMWF showing highs in the low to mid-50s amid a persistent cool upper-level trough over the Midwest. Recent scattered showers and cloudy skies through April 17-18, following severe storms on April 16-17, have suppressed daytime heating, with observed highs near 55°F on April 18—well below the 61°F climatological normal. Model runs indicate limited warm-up potential due to onshore flow and lingering moisture, though some ensemble members suggest a slim chance of mid-50s peaks if partial clearing occurs. Updated NWS forecasts and Sunday model refreshes will sharpen resolution as the date nears.