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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?

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    $\begingroup$ What do you mean by land ice? The seasonal variation in land ice is completely negligible compared to the total ice mass. Do you mean when the first non-melting snow falls? That of course depends strongly on latitude and elevation; in a cold enough climate, non-melting snow falls year round. $\endgroup$ – gerrit Jul 23 '15 at 10:07
  • $\begingroup$ I hope I've edited clearly enough. $\endgroup$ – user3224 Jul 23 '15 at 21:47
  • $\begingroup$ Complete sentences would really help. $\endgroup$ – farrenthorpe Jul 24 '15 at 16:04
  • $\begingroup$ I thought not having run-on sentences would help too. $\endgroup$ – user3224 Jul 24 '15 at 17:13
  • $\begingroup$ But I think I figured out ones that are brief enough. $\endgroup$ – user3224 Jul 24 '15 at 17:14
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A little Google searching and I found this:

enter image description here

Source: https://nsidc.org/cryosphere/sotc/snow_extent.html

Snow-cover is considered an important factor in climate change study, so it's tracked pretty carefully. There's probably a specific average minimum date out there somewhere if you're really interested but I didn't see it. Judging from the chart, somewhere around mid August.

Sea ice cover is later, that reaches a minimum in September most years, but oceans are slower to change than land and air, so that should be expected. The hottest day on average, if you care about that, is July 24. http://m.weatherbug.com/weather-news/weather-reports/5225

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