"Running throughout the book, he says, is a gentle quest to overturn the malign understanding of clouds that has long informed western thinking. "People do have a slightly derogatory view of them," he says.
"When people say someone's got their head in the clouds, it's about being disengaged from the world. Whereas I say, 'Sod it - what's wrong with having your head in the clouds?' It's a really important thing to do, a reaction to the pressures of modern life. But there are all kinds of negative associations: the idea of someone having a cloud hanging over them, or clouds on the horizon - these very doomy things.
"But there's an Arabic phrase for someone who is lucky or blessed - they say, 'His sky is always filled with clouds.' It's the complete opposite. Clouds provide shade and rain. And rain is life; it's about abundance. Clouds bring beauty to the sunset. And they clear the atmosphere. They're purifiers: cloud droplets form around bits of pollution and bring it back to earth. But one of the main things for me is appreciating their beauty. Every day is like a new page."
As far as Pretor-Pinney's life is concerned, clouds have had one particularly important effect. He met his fiancée, Liz - to whom The Cloudspotter's Guide is dedicated - at his first cloud lecture; their relationship took flight at a second meeting, where her opening gambit was, "You're the cloud guy, aren't you?"
That's so sweet of him and before I sign off, I wish that your sky are filled with clouds ;)