Paris hosts 2 festivals in this guide, in Île-de-France: We Love Green, Solidays.
Paris has 2 festivals in this guide. They run in June, and festival-day temperatures range from 24°C (75°F) to 24°C (75°F), with nights down to 14°C (57°F). That range is the reason there is no single "Paris festival outfit". The answer changes by month and by site.
Conditions are moderate across the board, so the day-to-night temperature drop is the thing to plan for rather than the weather itself.
The ground matters as much as the sky. You will find forest and open field, which puts broken-in trainers or a low boot at the top of the list for most of these events. None of them have camping on site, so you are travelling in and out each day and the outfit has to survive the journey at both ends.
Stylistically the crowd here leans indie, streetwear, techno and elegant. Solidays is the largest of them at around 60,000 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.
