Most notably, it's darker for later into the early hours of the morning.
Here in California, we observe a time mechanism that alters the time on clocks watches etc for part of the year.
Anyway, soon enough we'll turn our clocks back one hour, but until then - it's dark pretty late. Well, later than it was earlier in the year.
Beside all that, there's a hint of autumn in the air, but only a subtle and vague one... It's not yet truly old enough for a sweater in my opinion, but I see people getting out their puffer coats and the store where I work is pushing hooded sweatshirts.
The air temperature is still hovering between 70℉ and 80℉ though through the afternoon. (Fahrenheit)