Black Powder Sensitivity
iowa is exactly right.
Your sight wettings WILL change, but they will change in the same direction as if the temperature caused an increase in the powder burning rate.
That is, if an increase in air temperature made the powder burn faster and increased your muzzle velocity, the increase in temperature will also decrease the density of the air, resulting in less air resistance, and making your bullets strike higher on the target.
You can't separate the two. The only way to tell for sure is to use a chronograph. From the limited chrono testing I've done on this, I would say that the air temp has only a minimal effect on MV.