It always seems to me that it is very hot on the Minnesota Black Bear Opener. I thought it would be interesting to see if it actually was. Here is some data from the Farmers Almanac for Grand Rapids (Zone 26), MN. I understand that the temperature is very different in other parts of Minnesota, but here is a frame of reference.
The average high temperature is 75.7°F, a low of 53.8°F with an average harvest of 291.5 bears from Zone 26 each year since the Minnesota Department of Natural Resources (MN DNR) started recording data.
So it is not all that hot and it is reasonably cool in the evenings. You can review the numbers and come to your own conclusions. I see that hot years have fewer bears harvested and in cooler years higher success. You have to take into account the entire summer and food available. Best scenario is little food with a cool opening day.
It is going to be interesting this year to see the harvest numbers since there are fewer hunters and the number of bait sites allowed has been reduced to three per hunter. As most bear hunters know the opening success rate drops exponentially after the first day. If you are lucky enough to be in an area that there is little pressure you should have little to worry about.