Funny you should mention it, Baz.
My partner Rae and I were having the same hissy fit the other night.
We were commenting on how "amazing" it was that the days here in Canberra are perfectly clear and then sunset sees the cloud appear with cruel timing.
The other night, I swear there was not a cloud in the sky in the area of the comet and then just when it would have been showtime, the smallest patch of cloud developed to perfectly obscure the comet and was then joined by other patches out of "nowhere".
All other areas of the sky -clear!!!!!
What can you do?