Uhm... Cooler air = more boost... I thought it was relatively easy to translate?!

I'm not a meteorologist, nor am I claiming to be a scientist - but IIRC it works something like this: The cooler air temps allow for colder air to be drawn in thru the intake, thus lowering density charges received thru the blower, thus making the blower a bit more efficient (especially since it's a roots type blower) - thus noticing a small gain of a pound or two of boost.