Yes because modern Scandinavian homes have huge uncovered well insulated windows to allow the sun in as a free radiator during winter. I calculated my living room window to be somewhere between 3000W-5000W worth of radiation. Due to the high insulation this doesn't dissipate during the night in a heatwave, so it doesn't matter if the outside temp is 18°
Why? Because housing regulations dictated it. No one expected 2018 levels of heatwaves to be the new norm (except all the experts).
My old apartment reached temps of 35° measured at midnight for weeks in the 2018 heatwave despite the outdoor temp not rising much above 30°. Morning temps where around 28° with all windows open. If the morning baseline was lower the night temps might have been possible to sleep in but the insulation kept temps high throughout.
I live in a rental on 4th floor, unfortunately I can't add anything to the outside of the windows... And putting anything on the inside risks trapping the heat in the glass and cracking it.