I walked it in late June this year, so not August but still summer. The first day was very hot and that stage is an often shadeless walk with not much water available. It was quite hazy in the first few days and every afternoon/evening storms were forecast, but each of the first three days the rain didn’t come (although it got slightly cooler as the altitude increased). Finally the rain came on the afternoon of day 4 and it was much cooler after that.
I started on the Salvador on the first day of June 2019. I had been on the Francés up to León, and a heat wave was just starting. Going up into the mountains on the Salvador saved me from the worst of the heat.