Reading hosts 1 festival in this guide, in Berkshire: Reading Festival.
Reading has 1 festival in this guide. They run in August, and festival-day temperatures range from 22°C (72°F) to 22°C (72°F), with nights down to 13°C (55°F). That range is the reason there is no single "Reading festival outfit". The answer changes by month and by site.
1 carries a high rain risk, which makes waterproof footwear a requirement rather than a precaution.
The ground matters as much as the sky. Every festival here is on open field, which puts waterproof boots at the top of the list for most of these events. 1 of the 1 has camping on site, so outfits have to survive living in a bag on the ground for several days.
Stylistically the crowd here leans punk, alt, grunge and camping. Reading Festival is the largest of them at around 105,000 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.
