“Definitely correct; just the way it should be. It could just as well be ‘right as clouds’ or any number of other things, but ‘rain’ it is, doubtless because of the allure of alliteration” – The Dictionary of Cliches by James Rogers
The Guardian offers this explanation of the phrase’s origin.
Great name for your blog Jean. You have done a great job with the website – I really like the photo of you and Ginger too. I look forward to reading your blog and seeing more of your wonderful work :).