What to wear to Riot Fest: Chicago sits at 24°C (75°F) by day and 14°C (57°F) at night in September, on city park, with a moderate chance of rain. That means a light base with one warm layer you can carry, cushioned trainers or a low boot, and a bag small enough for the gate rules. The crowd leans punk, alt and grunge, so anything that survives the day reads as right.
Men's festival dressing at Riot Fest comes down to three decisions: how much you can take off when it hits 24°C (75°F), what you put back on at 14°C (57°F), and whether your shoes can take city park for 3 days.
The dominant aesthetics at Riot Fest are punk, alternative, grunge and rock. That is the visual language of the site, the stages, the merch, the crowd photos, and outfits that speak it look intentional rather than borrowed.
There is no enforced dress code. What the crowd rewards is a look that survives 3 days of city park without you having to protect it.
What people actually wear: one good layer over a light base, because the temperature halves after sunset.