Apres moi, le deluge

We're only in the first day of August, but already the leaves are starting to turn a rich, lush red. Autumn is on its way.

In the USA, of course, they don't call it "autumn". They talk of "fall", presumably because that's what the leaves do.

We have a wonderful adjective, "autumnal". It can be applied to colours, or weather, or anything that reminds one of autumn.

Is there an American equivalent for this word?

Fallal? - no, that sounds horrible
Fallish? - sounds too like foolish
Fallic? - I trust not...