My kid also did MS track/XC and plans to do HS XC. The apprehension at our house is about practice 5x a week on top of a club sport.
Sharing in case it's helpful that kid has already talked to HS coach, who said that daily attendance is still expected, but that practices would be modified (strength, stretching instead of running) on days with another sport practice.
Also fwiw, summer practices/tryouts likely to be early morning, 7am-ish (which may be a problem for different reasons, though perhaps less hot).