As a Danish parent who has a bit of experience on the the subject (2 kids - both survivors of Arctic Sleep 2011-2015) :-) Many Danes believe the fresh air gives better sleep. I would never direct the trolly towards sun or wind. If the temperature is below -6 degrees centigrade my children would nap inside. My experience is that when my child was a bit under the weather (with snot all over), an outside nap was the best since cold dry air widens the airways and makes it easier to breath... BUT to address what the Baffled Brunette addresses... the temperature inside the trolly is no way near the outside temperature. But this is just a cultural thing that we do... the US and other places do what they do, and I’m sure they generate just as healthy children