In article ,
Colin Youngs writes:
Op donderdag 14 november 2013 10:57:52 UTC+1 schreef John Hall:
On a clear night it's quite possible that there was a ground frost when
the air temperature as measured at the proscribed height above the
ground fell no lower than 2C.

... at the prescribed height ... :-)

Oops! You're quite right of course.
--
John Hall "He crams with cans of poisoned meat
The subjects of the King,
And when they die by thousands G.K.Chesterton:
Why, he laughs like anything." from "Song Against Grocers"