Can I open a window on Shabbos if it’s hot, if there is a fear that it might blow out the candles?
If the candles are placed opposite the window in a manner that if there would be a typical draft from that direction it would inevitably extinguish them – even if there’s no wind outside currently – it is forbidden to open the window.
If the candles are positioned in a manner (e.g., if they are in a distance) where a typical draft would not extinguish them, or if it’s in a season where a common draft of that time wouldn’t extinguish the candles, one may open the window.
רמ״א או״ח רעז, א. שוע״ר שם א. קו״א א שם. ערוה״ש שם ו. קצוה״ש קו בבדה״ש יא. וראה 28604: