In general temp and humidity variations go like this:
Colder air is denser. Therefore you have to richen the needles.
Wamer air is less dense. Therefore you have to lean the needles.
Humid air is less dense. Therefore you have to lean the needles.
Dry air is more dense. Therefore you have to richen the needles.
I don't have a way to tell you how much to change for <x> degrees of change or <x> percentage of humidity change. What I know from my V-Specs is that they're not very sensitive in that regard. I might have to change up to a quarter turn when going from 70 degree air to 40 degree air. I've never felt the need to change tune due to humidity.
If you run at different tracks, you're going to want to retune anyway due to the different track layouts. Don't be afraid to just try needle changes to see what they do. Starting from pig rich on the high end needle and leaning down until the motor is REALLY singing (then backing off of that about two hours) taught me a LOT about my engines. I found out I have a 120-150 degree window (4-5 hours) where my engines run from good to great.