Flower color tone

Those two photos have very different color schemes, but even so, I think either would be absolutely fine for a summer wedding. September 5th is still summer by the calendar and by your local weather.

Edited to add: I think those are yellow tulips in the 1st pic, which probably won't be available in September. The colors are fine, but it's always best to go with what a local florist recommends for type of flower available for the time of year.

If you love it, then go for it! I think that color scheme will be fine, considering it will be so warm still around that time of year (I'm from GA, so I feel ya!). Between the two photos, I personally love the second one the best. I feel like the shades it has in it are more representative of fall than the first bouquet!

Honestly when it comes to style, the most important part is what color scheme you like not what season it may represent. If you like spring/summer colors, definitely do them even if it's fall! Talk with your florist. They may say that they can do the colors you want but it'll have to be different types of flowers that are actually growing during September.