It seems to be a big problem with lots of discussion on line. The turf being a dark color absorbs a lot of heat and the packed infill retains heat. The solution it seems is evaporation just as in real lawns.
The article linked above seems quite logical they are eliminating the stone infill and using a cork product that retains moisture better and allows evaporation you still would need to water the turf some.
I also saw the crumb rubber used on top of the turf when heated very hot like yours can break down and pose a health risk for children and they are suggesting a cork fill product there as well.