Mid September is a super time to travel in Iceland.
No snow melt, low glacier run off, wonderful autumn colours (Salix Polaris especially) and
the night goes dark which means you'll get to see the northern lights (with a bit of luck)
And once in town or at tourist places; less tourists and all the positive aspects that come with less tourists
One of the down sides is there's little traffic on some routes in the interior. If you mess up it can be more difficult to get help (not every one is happy to press SPOT button...)
jam bo wrote:i think both those videos are shot around the llanmanalaguar trail. that is nowhere near the glacier 360 route.
Roughly. Looks like Fjallabak and Thorsmörk region, but yes, nowhere near the 360 route
This is on the Kjalvegur hiking/horseriding trail which is most likely part of the 360 route:

Good thing is, this lovely track brings you to Hveravellir (pron. Kveravetlir).
The Kjalvegur used to go across the interior all the way to the sea. Forth following the old Kjalvegur track. It gets emptier. I didn't see anybody for 80 km. The fords you come across are okay at that time of year.
I went to Iceland 3 times, once in winter, twice in Aug/Sept, once for a traverse on foot (ca. 650 km) and once for a double traverse by bike (ca. 1100 km)
This is just outside the remote and lovely Laugarvellir hot spring (nothing to do with Landmannalaugar):
I spent two months total in Iceland, albeit not July, and never felt wind drop during the night. Why should it?