Just back from Arles where it was over 40C on a couple of days and those were when the breeze stopped too. All the Rencontres visitors were walking around all day, though probably on the shaded side of the streets. It was easy to figure out which exhibition spaces were temporarily converted from some other purpose (ie. having inadequate ventilation for large numbers of visitors), simply by the rate of sweat-drips.
For making pictures, the morning and late afternoon were often better so far as the light goes - but the temperature didn't change much until after 8pm or so. My favourite accessory was a big wide hat. It remains to be seen if all my film survived being out-and-about and/or sitting in the tent, but I am not expecting problems with such non-extreme temperatures. (Famous last words).
