What's the average day of the year when the fewest square miles of the hemisphere's land is covered by snow or ice or transitional forms like slush? Not counting anything below ground like permafrost or uh, temporaryfrost.
Maybe the land minimum is pretty late since North Pole air temps seem to flatline near freezing for ages? That seems to imply there's enough insolation to make it above freezing in the Arctic for quite a while if there was no snow or ice there to chill it by melting. So maybe the last non-permanent snow finally melts in late August or September or something and the ground has like 1-2 weeks before avg temps reach freezing again?