Well I also wanted to know how temp and humidity will impact MV and ME when you fire them in Alaskan type cold and Arizona tyoe dry hot weather.
It depends. There is at least one manufacturer making ammunition which they claim will not change velocity based on temperature.
A chronograph is really the way to find out how ammunition is affected. But that's not always possible.
You will need to modify both the velocity and ballistic coefficient. Here are some formulas that should get you in the ballpark--but understand that they are only approximations.
SAAMI mandates that velocity measurements should be made at 70 degrees F. Therefore, for an approximation of velocity based on measured temperature you can subtract 2fps from the specified velocity for every degree Fahrenheit under 70 degrees or add 2fps from the specified velocity for every degree above 70 degrees.
Ballistic Coefficients are measured at 59 degrees F and 29.53mm of mercury. If you have a ballistic coefficient, you can adjust it using the following formula.
The correction factor for temperature is the current temperature in degrees Fahrenheit plus 459.4 divided by 518.4
Temperature Correction Factor = (Temperature in degrees F + 459.4)/518.4
The correction factor for barometric pressure is 29.53 divided by the current barometric pressure in mm of Hg
Pressure Correction Factor = 29.53/Current Barometric Pressure.
Corrected Ballistic Coefficient = Nominal Ballistic Coefficient x Temperature Correction Factor x Pressure Correction Factor
Here's an example.
The bullet you are using has a nominal ballistic coefficient of 0.50 and the U.S. ammunition manufacturer states that the muzzle velocity is 2700fps.
You will be shooting at 15 degrees F and 30.5mm Hg pressure.
First, correct the velocity. SAAMI velocity measurements are supposed to be made at 70 degrees F. 15 degrees F is 55 degrees below that and we assume a loss of 2fps per degree. 2 x 55 is 110 so we assume that the actual muzzle velocity at 15 degrees will be 2700fps - 110fps = 2590fps.
Calculate the temperature correction factor for 15 degrees F.
Temperature Correction Factor = (15 degrees F + 459.4)/518.4 = 0.9151
Calculate the pressure correction factor for 30.5mmHg.
Pressure Correction Factor = 29.53/30.5 = 0.9682
Now use the Correction Factors to adjust the Nominal Ballistic Coefficient.
Corrected Ballistic Coefficient = 0.5 x 0.9151 x 0.9682 = 0.443
So we went from a BC of 0.5 and a muzzle velocity of 2700fps to a BC of 0.443 and a muzzle velocity of 2590fps.