You should open the window in late spring and close it in early fall.
Old attic windows opening.
And if necessary i d keep them open just a crack until you can get some roof vents in place or gable vents.
If you leave the attic windows open be sure and staple some screens over them maybe even hardware cloth would be better to keep the critters out bats and raccoons etc will invade your space and give you fits.
2 are ornamental and the other 4 are regular functioning windows.
A broken window glass of the attic room of a house with the red shingles roof.
Thoughtful young woman looking at camera from the window of an attic at sunset.
An oval window wooden.
I cant think of a single reason tho close it all summer unless theres a big storm.
We have a large full attic.
Blur background of the city and buildings.
It gets stifling and stale up there if we don t.
It will vent heat out morning noon and night.
The windows have screens.
When the attic becomes part of the home to be heated and cooled open wall gable vents and roof vents are no longer feasible but the underside of the roof the sheathing and rafters can still.
The attic needs to be as close to the outside temp as you can get it year round.
If so you should keep the windows open both winter and summer.
6 windows in all.