Barcelona hosts 2 festivals in this guide, in Catalonia: Primavera Sound, Sónar.
Barcelona has 2 festivals in this guide. They run in June, and festival-day temperatures range from 25°C (77°F) to 26°C (79°F), with nights down to 18°C (64°F). That range is the reason there is no single "Barcelona 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 city streets and industrial site, 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, alt, streetwear and elegant. Sónar is the largest of them at around 120,000 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.
