Traction Control Light and Brake Lights Stay On

But only when raining hard or with a lot of road spray. I have about 250K miles on a 2011 Prius 5. For example yesterday I drove through rain and roadspray. Got home. About an hour later went to get mail and noticed the brake lights flickering. Watched for five minutes, no flickering. Went to let the cat out and my brake lights were on. This has happened twice before, but becoming more frequent. Now I also get the traction light icon on the dash. After driving in dry weather and using brakes frequently all returns to normal. I assume a sensor is having an issue. I commute on a well salted road 5-6 months out of the year. Anyone have an idea or point me in the right direction? I appreciate it.