A squealing disc brake does not always point to the same problem. SRAM says water or dirt on a rotor can temporarily make previously quiet road-bike brakes noisy. If the sound follows a wet ride, the first step is to inspect the brake and clean the rotor with isopropyl alcohol or mild soap and water, as the manufacturer recommends.
Noise that persists is a different matter. The pads may be contaminated, or an improper bed-in may have left an uneven layer of pad material on the rotor. For its road disc brakes, SRAM recommends replacing the pads and rotor in either case, then bedding in the new parts carefully. Cleaning alone will not fix every cause of lasting brake noise.
During bed-in, pad material transfers evenly to the rotor’s braking surface, helping the brake deliver consistent power with less noise. If braking feels weak or the lever pulls close to the handlebar, the sound should not be treated merely as an annoyance. Pad wear and the wider brake system need attention; when the cause is unclear, a qualified bicycle mechanic should inspect it.