The Chicago Marathon, held annually in Chicago, experiences a wide range of weather conditions and variations on race day. The race typically takes place in early to mid-October, when fall is in full swing. On race day, participants can expect crisp and cool mornings with temperatures ranging from the mid-40s to the mid-50s Fahrenheit (7 to 13 degrees Celsius). However, as the day progresses, the weather can quickly change, and temperatures can rise to the mid-60s or even low 70s Fahrenheit (15 to 22 degrees Celsius). Additionally, participants may encounter gusty winds from Lake Michigan, which can vary in strength and direction. Over the years, the Chicago Marathon has also experienced occasional rain showers, drizzles, or fog, adding an element of unpredictability to the race day weather. Therefore, while the mornings often start chilly, runners should be prepared for potential weather variations and plan their attire accordingly.