You can change your water and your yeast based on the weather. There is really no answer to how much exactly it should it be. I wish there was a simple formula, but you have to understand that water temp, yeast amount, air temp, bulk temp, fridge temp, final rise temp, humidity, mixing time, etc etc all play a factor and prevent an exact formula that can be used by everyone. Each person kind of has to discover theirs for their area, workflow, and conditions.
The % of yeast is based on the days you would like to ferment your dough? or how is yeast calculated for a recipe.
In general, all things being equal, you use less yeast for a longer ferment. But a 24 hour room temp ferment may have less yeast than a 3 day cold ferment.
I know there is really no answer in my post, and for that I'm sorry. What do you specifically want to do? Maybe then I can give you a more specific answer.