Yesterday evening it was really hot outside, like being in a warm bath. Today looked at first as if it was going to be worse, but altocumulus castellanus appeared and it duly thundered. I wish I'd learnt about Ac cast. earlier, I'd never heard of them till I was reading ahead in a geography textbook when I was about 14. Since then I've found them an infallible thunder-predictor.

Trudged home from work in the heat.

0600 0
0700 6 Ac, Cu, Ci, Ac cast
1000 THUNDER SHOWER
PM ~4 Ci Sun
HOT