A Magical Kick-Off

OK, just a short, late-night heads-up on what miraculous thing just happened - and I don't know how it can work. 
My man and I have just returned from a walk (we like walking around in the dark and glimpse into other people's houses - and I swear it isn't as creepy as it sounds) and we noticed something quite peculiar. From all the cars standing around, some were completely soaked in rain whereas others - standing right next to them - were all dry...
How can this be and which magic is going on here??? Alright, maybe I am slightly preoccupied by the thought of magic as I just finished watching the series Mr Norrell and Jonathan Strange, positively the most peculiar mini-series I had the honour (or dishonour, I haven't yet decided) to watch. 
Either way, I decided to take this as incentive to kick-start my Harry Potter weeks tonight. As you should know, Harry-Potter-Day is looming. On 31st July, it will not only be Harry's birthday, but also Jo Rowling's, so I thought to concentrate on some HP related issues in the next few weeks. 
On Facebook I follow a thread which issues new HP content every day and I found a poster with 30 Harry Potter questions to be answered and I will answer one every day, commencing today. Have fun and let the magic begin! (And should you have an answer to the car mystery, please comment!)