Spot on Derek,
My usual corrective action if this problem arises is to take the vehicle out onto a suitable length of lightly used road and do about 4-6 hard stops [i.e. the wheels are close to locking up and the ABS does not activate] from 80Km/hr. Drive the car home, allow the brakes to cool and give the callipers [both front and back] a good wash with a hose nozzle through the wheel from outside and behind from under the wheel arch to wash out the dust. Let the brakes dry and then do one or two average stops to warm them up to evaporate any residual moisture. If you do not do this and leave the car overnight or longer after washing the callipers, it is possible the rotors will develop some light surface rusting and a grating noise might be heard on the first one or two brake applications until the rust dust is ejected from the pads.
The problem is more likely to arise with "hard" [premium performance] than with "soft" brake pads.