Late August thunderstorms usually hit in the afternoons. If you start at midnight and make reasonable time, you can summit and be well on your way down by noon. Check the weather links on this site. The probability of storms is fairly accurately forecast a few days in advance.
I will let others comment on what ice and snow may remain in two weeks and what equipment would be needed to deal with them. I don't do winter hiking.
Mountains can have any kind of weather any time of the year without much warning. Bring layers and a waterproof, windproof outer shell.
