I find that September is often better overall than August here, although my point in the chart that I posted was in reply to the September warmth was highlighting the sub528dam air in northern parts of Shetland. 

Mmm... (where's the drool emote?)

Amazing, frankly. I don't think I've ever seen a GFS chart bringing the -5C 850 line across Scotland from a run in August before!

http://www.wetterzentrale.de/maps/GFSOPEU06_384_2.png

537dam in the far north too:

https://www.theweatheroutlook.com/charts/gfs/06_384_ukthickness850nohd.png?cb

Fantastic stuff. I would imagine that has about as much chance of coming off as a win on the National Lottery tonight!

Gone on the 12z update as expected. Nonetheless I have a gut feeling that September could deliver an early and "potent" cold snap.  

Bit of a model divergence for Sat 1st Sept - 7 days time . . .

GFS hangs onto the dry, warm and settled theme: http://modeles.meteociel.fr/modeles/gfs/runs/2018082518/gfs-0-162.png?18

ECM looking more unsettled: http://www.meteociel.fr/modeles/ecmwf/runs/2018082512/ECM1-168.GIF?25-0

More so with GEM: http://modeles.meteociel.fr/modeles/gem/runs/2018082512/gem-0-168.png?12

Still a little beyond UKMO's range, so I'm still no wiser with the forecast for my nephew's wedding on that day.

ECM has joined GEM this morning. All a question of whether that small but potent depression moves in a sits over us, or as GFS has it, stands off in the Atlantic and brings up aoutherly air. See T+216.

What do you mean by potent for early September?  I would describe it as low double figure maximums by day and single figure night time minimums with ground frosts in places and possibly an air frost in one or two areas.

I was thinking of the possibility of snow falling to lower levels in the northern half of the UK at some point in September. Also I meant early in the context of the meteorological autumn, not the month. 

My goodness - that's more intense than I would have thought. I can well imagine that is possible though.

Has that even happened before? It's hard enough getting snow before December - it's very uncommon in November and very rare in October (I can count on one hand the number of times I have seen snow falling in October in my lifetime).

1919 and 1952 I believe but it is exceptionally rare. 

If I remember rightly though, it has even been known to snow in June before even though it is very rare for that to happen.

According to the UK Met Office:

On 25 September 1885 snow was reported to have fallen at London and Wallington in Surrey making it the earliest fall of snow on the capital

I wonder if snow to low levels has occurred more in June than September. I wouldn't be surprised if that was the case..

The year my gran and my mum were born, respectively. An amusing coincidence!

As Brian says, sleet has been recorded in London in September in the 1880s - along with sleet in July. It's one of those things that's possible, but incredibly unlikely. Further north the odds have to be higher, but still pretty small.

Even the talk of snow in October to me seems amazing simply because it is so rare, so the thought of snow or even sleet in September seems unthinkable. 

The October 2008 snowfall is the best example down here in recent times:

https://www.theweatheroutlook.com/twoother/twocontent.aspx?type=bg&id=1680

https://www.theweatheroutlook.com/twoother/twocontent.aspx?type=bg&id=1681

However, it also snowed in October 2010 as well I think. 

It's snowed in 3 Octobers here since 2010, I think.

Last year we had snow in every month from November to May.

North Pennines about 6 years ago about 7 June. It maxed out at 6°C here in Durham, went up to the Pennines and there was snow at around 3°C.

I remember snow in October twice - first was 2000, and second was I think 2015. Both occasions were just a bit of short-lived light snow at the end of the month, neither settling.

I have no clear recollection of snow falling to low ground in October in my neck of the woods in time in the past, but we have had some pretty chilly days for sure especially late on in the month. October 2008 for example, which ties in with the very early snowfalls that some aread in the south saw then which Brian mentioned above.