We always used to say sailor's delight, being brought up near the sea I suppose with strong maritime leanings in the family, though Richard Inwards' Weather Lore (1893) would confirm this:

Sky red in the morning
is a sailor's sure warning;
Sky red at night
is the sailor's delight

I believe shepherd's delight to be the more common, hence:

If you empty your bowels at night,
A shepherd will have a red face in the morning.

(Ivor Cutler)