Okay you win. 😀🤣

I imagine there could be higher gaps in summer when the south gets up into the 30s and the northern isles are cool, but it can't happen very often?

The gap between highest and lowest minima last night was even bigger, -13.3C at Loch Glascarnoch and 11.4C at St James's Park.

Edit: Parts of Northern England could see as low as -17°C.

Here's a screenshot of Darren Bett saying much the same this afternoon... "could get REALLY cold", as he explained! (Love the expression on his face too!)

https://ukwct.org.uk/weather/reallycold.jpg 

The SE England forecast from the MetO is as follows:

Staying cold with severe overnight frosts.

This Evening and Tonight:

Dry with clear skies overnight, which will lead to a widespread and locally severe frost. Winds falling light inland but staying breezy along the north Kent coast. Minimum temperature -5 °C.

...

Outlook for Thursday to Saturday:

Staying dry with some decent spells of winter sunshine on Thursday. Staying cold, with widespread and locally severe frosts overnight. Turning cloudier from the west Friday and Saturday. Light winds.

The question is - what do they count as a "severe" frost? I know of course of ground and air frosts, of penetrating frosts (where there's a wind), but I can't see what makes a frost "severe". Apparently the Finnish Met Office regards -15 as severe, but that's not much help!

Does anyone know the cut-off? And if -5 is "severe", what the heck is the -15 to -20 that we might see up north in a couple of days?!

EDIT: There is mention on the MetO site of "very severe frosts" in previous events, but again no definition. And their education section says that high pressure means "Severe nighttime frosts can develop if skies are clear" - but again no definition. Pah.

https://www.weatherdiary.uk/2023/11/04/the-definition-of-freezing-and-what-constitutes-an-air-frost/ 

Ahh, well found! 👍

So... -2.5C to -5.5C with a wind of 10 knots or more is "severe", or -6.5C to -11.5C without the wind.

And that also means that back in 2018, when it was a gnat's whisker away from -15C here, it was "very severe".

What a shame the Met Office don't stick that on their website, but it's a similar thing with the definitions of "cold", "exceptionally mild", "warm" and so on - I have to refer to old forum posts or Usenet posts as a reference.

This met office twitter post might help..

https://x.com/metoffice/status/1876645177609109657 

-8C in south Thursday night and -16C in northern England 

Monday night it barely dipped below freezing. 

Only -1.9c this morning here, LBA is -1c , yet the Met Office App says -5c there right now. 

So not expecting -7c to -10 in the next few days as the Apps show. 

An honourable mention for the Cairnwell which recorded a wind gust of 111.2 kph at 9am with a temperature of -5.3C. That'll feel a bit fresh.

It was -5c at 6pm so will be interesting to see what it gets down to tonight, given we have more extensive and a little deeper snow cover.

Even here, I was hoping to beat last year's low of -3.9, which shouldn't really be too much to ask, but it's only gone as low as -2.4 so far.

There are a few hours left of cooling to come, so we may yet see colder values, but even so it'll have to drop a fair bit to get to the levels forecast over the snowfields in the north.

The models, I would suggest, haven't covered themselves with glory in terms of night time temperature forecasts!

To be honest I was surprised at the -15°C to -20°C forecasts as I don’t believe that ever looked likely under last night’s conditions. I would also think that, in Scotland at least, tonight may be colder than the one that has just gone, with -15°C more achievable.

In Scotland it looks as if temperatures started to drop fast in the later stages of the night but the lowest so far looks like -11.8C at Resallach. Looking at the graph I expect it will drop further though. 

Quite a few local PWS in Inverness-shire have dropped below -12°C with the lowest at 13.5°C so far. If conditions had been favourable earlier some very low minima would have been seen. Depending on timing that may be the case tonight in Strathdon or Royal

 Deeside.