Dynamic pressure is greatest at transonic flight (Max Q), then reduces as the aircraft goes supersonic and accelerates past Mach 1.2.
Actually dynamic pressure continues to increase as the speed increases, while dynamic pressure decreases with increasing altitude (less density). The speed at which Max Q occurs is a function of the Mach/altitude profile that is being flown.
That being said, the center of pressure relationships move around in the transonic range, which can result in unwanted movement of the control surfaces when traveling transonic.