Yes Phonak Hearing Aids are waterproof and water resistant as well.
Well at least some of the Phonak Hearing aids are.
Phonak has made a line of water resistant and waterproof hearing aids so they can be in the water without damaging them.
For non water resistant and waterproof hearing aids the humidity can affect the hearing aids and how the hearing aids operate.
When the weather is humid the humidity can cause moisture buildup in the hearing aids which can make the hearing aids stop working or cause the hearing aids to not work as good as they should.
The hearing aids may not be as loud or you may notice a squealing noise or screeching type noise from the hearing aids.
That could be caused by moisture buildup.
You can help get rid of moisture from the hearing aids by putting the hearing aids in some uncooked rice.
The rice will help to draw moisture out of the hearing aids.
If moisture is allowed to get into the hearing aids and the moisture is not removed then the hearing aids could stop working completely.
If it's raining out it may be best to remove the hearing aids until you get out of the rain.