Every time it rains, the alarum of my 04 Prius goes off. Usually in the middle of the night. The garage says that the internal sensors are the cause and are trying to find if TOYOTA has a solution. Meanwhile, I am to switch off the internal sensors by pressing the button located under the steering column every time I leave the car. Seems to work and it doesn't affect the wireless locking or immobiliser. Any of you have similar experience or know how to fix it?