Chicago's August 20 High Temperatures Expected Below Seasonal Normals
According to the National Weather Service and ensemble models, Chicago's maximum temperature on August 20, 2026, is forecasted to range between 78°F and 81°F (25.6°C to 27.2°C). This is notably below the seasonal average of 82°F (27.8°C). A post-frontal air mass, increased cloud cover, and scattered showers are expected to suppress afternoon heating, limiting diurnal temperature rise. The most likely temperature bins are 78–79°F (52% probability) and 80–81°F (29% probability), with minor model spread around peak insolation. These conditions align with historical mid-August baselines for the region. 
