Will I be cold?
Will I be cold in São Paulo in September?
Verdict
No — No, comfortable.
Lows stay near 56°F — you won't be reaching for the puffer.
Day vs. night
Day
73°F
Warm
Breathable fabrics; sunscreen matters more than a jacket.
Night
56°F
Cool
You'll want a warm layer after sunset — not a heavy coat.
Why
São Paulo in September averages highs of 73°F, lows of 56°F, 8 rainy days.
You can pack for the daytime temps and not worry about the evening dip.