Many powders and expecially Ball types will have higher pressures when heated. If these rounds are on the ragged edge, keep them in the shade. You will know as the day progresses how they are doing. This is not just going to make an OK load destroy your gun on the first round. You will start to see pressure signs as the temps rise.
One word of caution, if your barrel and chamber is heated up, keep the bolt open till you acquire the target, close the bolt and take the shot. My nephew ruptured a 17 rem case a few years back with a peak load and froze the case in the bolt face. He had shot too long in high heat of north Texas. Loaded a round and began to look for another shot. Five minutes later he took a shot and ended that rifle for the day. The rifle was not damaged other than the ejector quit working till I took it out and replaced the pin and spring.
