What uwmgdman seems to be getting at there is "Humidity Ratio". HR is a measurement of humidity in the air that excludes temperature as a factor. Here is the calculation for humidity ratio (for degrees Fahrenheit):
HR =15432.3584*0.62*10^-5*0.01*Relative Humidity*(610.78*EXP(17.2694*((Degrees Fahrenheit-32)/1.8)/(((Degrees Fahrenheit-32)/1.8)+238.3))/2.2046).
You can plug that into an excel spreadsheet replacing Degrees Fahrenheit and Relative Humidity with cell addresses in which you've entered values for dF and RH.
This explanation still does not indicate temperature alone as a factor. In most cases, the HR of cold air is lower than the HR of warm air, hence the higher evaporation in cold air. But, if you compare the following 2 scenarios:
90dF, with 20% relative humidity = 41.47 humidity ratio
60dF, with 80% relative humidity = 61.10 humidity ratio
In this case, the warmer air has a lower humidity ratio and will allow for less condensation at the boundary layer (less water falling back into the pot) due to the lesser difference in boil temp vs. air temp. So, the 90dF air temp will result in a higher evaporation rate.
Like I said before, in most cases, colder air has a lower relative humidity and humidity ratio and will result in a higher evaporation rate, but colder air temperature alone does not result in a higher evaporation rate.