mini cooper cabby

[Mike Holmes]

I have just bought the wife a mini cabriolet 1 owner 34k on the clock 2004, its always been garaged by the old boy that owned it so its not seen much rain

Anyway to cut a long story short the cars parked up the drive , cars locked , it starts to rain very heavy and the alarm goes of , waking up my neighbours , any idea what is causing this and is it a common fault .

Is there a very sensitive sensor some where

Any help please

Thanks