He's probably not flying anywhere that it makes a difference. Hot air certainly does affect flying in many locations, mainly higher altitude airports. I imagine if he flies out of Denver in a heat wave, his answer would be different.

As for temperatures displayed on those outdoor electronic signs, I take them with a huge grain of salt. A lot of them read the temperature inside the unit and the sun beating down on it can skew the actual temperature. I've seen high 30's on those signs when it's really high 20's. (btw the forecast is back to mid to high 20's starting next week for southern Ontario, so get those flights booked LOL)