The temperature at Redfearns yesterday was around 26° celsius and I shot the course twice, once in the morning and once in the afternoon.
I used a Leupold 40x Competition scope on a Steyr 100 in the morning and the scope over ranged about a yard and a half at 55 yards.
In the afternoon I used a Nikko Sterling 10-50 mk 3 on a Steyr 100 and the scope over ranged four and a half yards!
As Tool said ALL scopes are affected by the heat, some more than others.
The Steyrs were unaffected by the heat.