Conor wrote:
It's usually chilliest just at dawn, or just after is it not?
No. It's between 4-5am.
Sorry, this just isn't true. It is coldest soon after sunrise
and I have 24 year's thermograph traces to prove it. There is no
reason why the temperature should rise before sunrise in the absence
of any change of wind or cloud.

Yebbut that doesn't take into account windchill.

I've spent years being at work at that time.

Windchill is ********. By which I mean that it doesn't actually convey
any useful information;
If it is +1C and there is a 'windchill' of 5 degrees, there wont be a
frost, as if it were -4C. If you wear windproof clothing then it feels
exactly the same as +1C. Obviously, air movement and humidity do have
an effect on your perception of temperature, but then so do your own
movement (standing still vs walking/running/cycling), clothing, skin
moisture levels, etc. - how much colder it feels than dry still air is
entirely subjective.

Sorry, personal bete noire. I'll shut up now...