Velux windows on 2nd floor open or closed during heatwave?

[IronHand]

It heatwave type weather (due to be over 30 here today) I close all the windows and blinds early before the house heats up and open them again in the evening. But I have a real dilemma over the large roof windows (velux) on our second floor. They have fitted blinds which I pull but I can’t help feeling that it would be better to leave these open - mainly because of the ‘heat rises’ logic.

Dh and I have this dilemma.
He agrees with your heat rising logic, I'm not sure.
Following with interest.

Open in our house.

If not facing the sun, open a crack to vent.
If facing the sun, closed

I would try both on consecutive days when you’re at home, and see what makes a difference to temperature.