It reminds us that even when tranquility seems to have vanished, it actually has not. It's there all along, and we can restore it by resting the gaze, stilling the breath, and seeing the clouds — the worries and troubles — for what they are: distractions.
This doesn't mean I put this metaphor to practice, but it's top-of-mind enough that when I look out my office window at thick clouds and an ever-shrinking patch of blue, I remember ... and take heart.