Hey Meerkat,
Air with water vapour in it is lighter than air. Sounds counterintuitive, but true.
From here:
peswiki.com/directory:enviro-mission-ltd-solar-tower the more the air can be saturated with water vapor the lighter it will beI'm always doubtful about the "Cold wind at 20 knots has more grunt than warm air at 20 knots" theory anyway, as well as the water vapour theory. To measure wind speed the wind has to hit the blades of a wind meter, so if it has more grunt then it will make the wind meter read higher, so as far as you can tell the "wind speed" will be higher. I fail to see how a kite and a wind meter would behave differently.
Also if you do the maths the difference between air at 10 degrees and air at 30 degrees is 3/8 of FA, the same goes for humid vs non-humid air.