Pack or skip
Insect repellent for Chicago in September
Verdict
Pack it
Warm (74°F) plus 9 rainy days = mosquito conditions.
Why
Chicago in September averages highs of 74°F, lows of 57°F, 9 rainy days.
That climate means insect repellent earns its space in the bag. Warm (74°F) plus 9 rainy days = mosquito conditions.