General rule of thumb for shooting. Not an exact science, but it is what is taught to military snipers.


From any given temperature the following will happen:

for every 20 degree increase in temp from your zero, you can expect a 1 MOA higher POI ( point of impact )
for every 20 degree decrease in temp, your zero will be 1 MOA lower


For given humidity:

For every 20 % increase in Humidity, round will strike 1 MOA low
For every 20 % decrease in humidity, round will strike 1 MOA higher.


And yes, they can work against each other. If you have a 20 degree increase in temperature, and a 20% increase in humidity, then there SHOULD BE no change.


Hope that this helps some. Good Luck.