What to wear to Portola Festival: San Francisco sits at 21°C (70°F) by day and 14°C (57°F) at night in September, on city streets, with a low 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 techno, house and urban, so black and functional reads as insider.
| Typical daytime high | 21°C (70°F) |
|---|---|
| Typical night low | 14°C (57°F) |
| Day–night swing | 7°C (13°F) |
| Rain risk | Low |
| Ground | Tarmac and pavement |
| Sun exposure | High, little natural shade |
Everything below follows from those numbers.