If you will be hunting in hot temps, you should be testing your loads in comparible temps. You don't want to be the guy who only gets one shot off then has to beat his bolt open with a rock. However, you will have trouble getting accurate groups at the range in hot weather as noted before, the barrel just doesn't cool down enough unless of course you have a cooling device. I've been testing handloads in 85 degree weather for my Yakima area elk hunt in Sept. I was looking for pressure signs due to hot weather with max loads. I found out what my max loads were but didn't get very good groups at that temp. I figured the barrel was getting too hot so I tried them again at 70 degrees and found that I had tight groups after all. Work them up in the heat and group them in the cool.