Do you sleep better with an open window?

Where I am, it's starting to feel like summer, and I'm sleeping with the window open! Now I wish I had a stream right outside to soothe me to sleep, or a fragrant lilac bush to fill the room, but even just the fresh air gives me a noticeably better sleep.  Is it just me, or is there some science behind it?

Cool temperatures make it easier to fall asleep.  That's per this 2012 study, among others.  And so depending on where you live, an open window might not make for a cooler night's sleep, but it does for me, right now.

Improved ventilation - fresh air! - makes a difference too, and there's research that open windows lower the amount of carbon monoxide in a person's blood, which is commonly linked to sleeplessness.

Going the other direction, allergies are a concern, even for me, at some points in the year.  When it's pine pollen season, windows closed!  And that's not just for my own health and sleep, but to make for less cleaning in the house too!  Depending on your location, highway noise could be a concern too. 

What about you, are you an open window sleeper during the summer, or even year round, too?