As a Millennial who has always lived in or around Chicago I can say that this is not natural. Despite the Midwest being the most climate-diverse region in the US we usually expect it to peak 90*F (32C) in July, not get above 90 in September. This year Chicago has had 19 days in the 90s, peaking 96* F (35.5*C) on 2 September, and likely not over. This is our hottest year since 2012, where we had 43 days 90 or hotter
https://abc7chicago.com/post/chicago-weather-forecast-heat-advisory-effect-friday-area-index-values-100/19788466/