Indio hosts 2 festivals in this guide, in California: Coachella, Stagecoach.
Indio has 2 festivals in this guide. They run in April, and festival-day temperatures range from 33°C (91°F) to 34°C (93°F), with nights down to 14°C (57°F). That range is the reason there is no single "Indio festival outfit". The answer changes by month and by site.
Every one of them run in real heat (28°C or more), where loose natural fabrics beat coverage and a brimmed hat does more than any garment.
The ground matters as much as the sky. Every festival here is on desert, which puts closed boots or trainers you accept will change colour at the top of the list for most of these events. 2 of the 2 have camping on site, so outfits have to survive living in a bag on the ground for several days.
Stylistically the crowd here leans desert, americana, boho and y2k. Coachella is the largest of them at around 125,000 people, and it sets the tone the smaller ones react to. None of that is a dress code. It is what you will see, which is worth knowing if you would rather blend in or deliberately not.
