I have flown using them at 1000m and noticed its a little more responsive. The extra pitch in cold climates will allow more of a response however, with warmer dry air Things change in your favour and become less dense so mitigating some of the extra pitch and reliving the load on the motors.
I have found an online calculator to help calculate air Denserty verses temperature, this will show how Density effects lift. http://www.engineeringtoolbox.com/density-air-d_680.html
Hope that helps a little..