What to wear to Notting Hill Carnival: London sits at 22°C (72°F) by day and 15°C (59°F) at night in August, on city streets, 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 carnival, costume and parade, so a full costume is the norm rather than the exception.
Women's outfits at Notting Hill Carnival have to clear the same three hurdles as everyone else's. 22°C (72°F) by day, 15°C (59°F) at night, city streets underfoot, with more options for solving them.
The dominant aesthetics at Notting Hill Carnival are carnival costume, full costume, parade and dancehall. 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.
This is a costume festival, and that changes the maths: turning up in normal clothes is the conspicuous choice. Budget for one full look rather than three half-hearted ones, and make sure you can walk, dance and queue in it for eight hours.
What people actually wear: one good layer over a light base, because the temperature halves after sunset; something identifiable, a colour, a hat, a flag, so your group can find you in a crowd of that size.