Complex sentence: Pressure may not be a good measure for rainwear, as the force of the rain drop on the fabric also depends on how much the fabric moves; it is a good measure for sitting on wet ground or similar situations.
Split into simpler sentences: Pressure may not be a good measure for rainwear, as the force of the rain drop on the fabric also depends on how much the fabric moves. However, pressure is a good measure for sitting on wet ground or similar situations.