I would say yes.
You will certainly get them to germinate and make good strong plants but to flower......? I think you have left it too late.

oooopps :-) I had some Cosmos seeds left, and a gap for filling in, so sowed some yesterday. So this can be a test case - I'll try to remember to report progress.

The amount of daylight is now dwindling as each day passes. Comos will grow but when the time comes for it to flower it will run out of gas.