Ok so had the cover on now all the time that torrential rain was gracing us so about 2 weeks or so. Took the cover off today and the roof was soaked, inside and out. The rain had obviously penetrated the cover. The sides were damp as well. In my opinion I don't think it's a good option in winter or very bad rain. Started up ok though so I took him for a wee blast now it looks like he's covered in salt.