Are you talking about a formula that you made for the first time? If so, you should not assume anything. There are so many variables between everyone's unique situation that any formula should be viewed only as a starting point.
If you are talking about a formula you make often, it's possible you might have to tweak the flour a bit. I have never found it to be necessary however. I would think it more likely that it would be as a result of a new bag of flour having a different moisture content than the humidity per-se. Yeast/culture on the other hand, I adjust with the seasons.