I can't think of many things which are so ordinary in themselves, yet which have been the carriers of so much poetic, literary, theological, spiritual, musical and psychological freight, than clouds.
A cloudy day may be something to lament, because we all supposedly want sun (if weather men and women are to be believed) but none of us can imagine a sky without those cloudscapes we've all stopped in our tracks to look up to, as the clouds of Michaelangelo's Sistine Chapel ceiling fill the mind's eye. Or maybe that only happens to iNtuitives...
It was Wordsworth who famously referred to 'clouds of glory' in his poem Intimations of Immortality:
'Not in entire forgetfulness
And not in utter nakedness
But trailing clouds of glory do we come
From God, who is our home:
Heaven lies around us in our infancy',
carrying with it the idea of the pre existence of the soul, an idea which is more Platonic than Judeo-Christian, but that's the Romantics for you.
I for one find it difficult to see clouds as just collected masses of water vapour with light shining off them, or through them, or whatever the scientific reason for clouds is. I just can't help thinking of all the other concepts associated with clouds: silver lining; glory; coming in the clouds; Son of Man; etc.
And it's all going on up there most days, take this evening for instance - it was, as Crowded House sang, 'Four Seasons in One Sky', as if were.
I admit there's a problem with the Ascension - Jesus going 'up', apparently into the clouds, his feet sticking out from the bottom of a cloud as his body rises up like Apollo 13... we come up against our conceptual limits when we try to imagine how spiritual realities exist alongside physical. Tom Wright puts it brilliantly in Surprised by Hope when he imagines Jesus' 'coming on the clouds' as a peeling back of this reality to reveal the reality of God's reign, in other words - he didn't go to a place - he is in another reality, which will become our reality at his 'return'.
All of which is to say there's a lot of other stuff apart from perhaps being about to rain, going on with clouds.