Well, its possible. Are you going to be 100% on it or are you starting a job? The ‘reasonably sure of passing’ part would depend more on how hard you study rather than a specific start date.
I’d start in August to be safe, but that’s just my opinion.
It really depends on your level of familiarity with the material and how much studying you do when you do start. You’ll need to make sure you set aside proper time if you start in Sept.