I would like to add that hot air is also more viscous; hence the drag by friction of the model is higher.
That is for the model.

For the pilot:
In hot and humid days down here in Florida, drinking plenty of liquid is not enough.
This is because the high humidity does not allow the sweat evaporation cool down the skin and the body enough.
Cooling down by splashing fresh water over the skin, using fans, and even stepping into the air conditioned car for 10 minutes may prevent passing out due to hyperthermia.