Let the heat escape
Blistering occurs when the tread block has an excessive amount of heat buildup and no way to vent it out. A bubble forms that eventually pops and causes a loss of traction and or tire failure. To prevent this your options depending on the tire rules allowed are as follows.
1. Reduce the tread block size by grooving through the center in any direction. Across the tire for added forward traction. Around the tire for added sidebite. Angle for a combination of both.
2. Using a router or compact cut out tool and a round 1/8" bit you can drill a vent hole in the tread block. Make sure set the depth no deeper than 3/4 of the available tread depth.
3. Using a grooving iron and a narrow #2 blade dip the center of the block.
4. Using a sipe tool cut a single circumferential sipe less than half of the available tread depth.
You might find that a combination of these is needed to achieve optimal performance.
Bonus Tip - Baby powder can reduce friction when grooving, siping and buffing. Making the task a little easier and a lot faster.