Weather in August

I don't think it will be "considerably cold" in August, although you may find a few nights chilly (near the pass and near Golinhac). (Bear in mind that as a Pacific Northwesterner my standard for "chilly" is something below 50 degrees F. Your mileage may vary.) You should expect one or two days of rain each week (at least be prepared for it). They have real rain: thunderstorms and gusty winds, quite the squall. I saw two that lasted entire afternoons and I was very grateful for having already reached shelter those days. It cools off the day after the squall line passes.

You do not need to take "semi-winter clothing" such as a fleece or a sleeping bag. But you will find long pants and a layer of T-shirt + long-sleeved=shirt + wind-shell under your poncho will be very adequate for what you face.