My guys were in a hoop house with the side propped up so they could get out. We had a short heatwave a few days before they were due to be processed and even in the shade, they were clearly uncomfortable. It was in the high 90'sF and very humid. I dragged a box fan out and directed it at where most of they were sitting. It did seem to help. While they still panted, they didnt look as distressed. I am also going to try to not have market sized birds at this time in July next year. I have little ones now and I think they will deal with the heat better than the big ones did. It should be a little cooler when they are ready for processing.
