I live in Sydney. Its hardiness zone is 10b-11a (depending on the region). This autumn thus far has been warm and sunny with temperature range between 28C to 13C on average. Not too hot and not too cold. But my Four O'Clock, after flourishing in the hot summer, is now not flowering and its seed pods are yellowing. It is rather large in shape, if that helps.
All I know is that Four O Clocks 'die out' in the first frost, but we don't even have frost yet. And, as said, the weather these days has been rather warm. So what is going on exactly with the plant?
P.S. I have another large Four O'Clock in the front yard that is still flowering at parts. It acts as an annual, dying in late autumn and reemerging in late spring - Even though we live in a warm hardiness zone.