In message , Vidcapper
writes
On 01/12/2020 09:46, Bernard Burton wrote:
"Keith (Southend)" wrote in message
...
This November I only had two 5 minute logs (10 minutes) of 0.0°C, is this
classed as an air frost or should it be -0.1°C?
My thinking is not, so no air frost reported for me for the whole month.
Keith (Southend)
Yes Keith, temperature needs to be below zero to warrant a frost
Try convincing the local car owners of that, though! 
The temperature of car windscreens, and even more so car roofs, is I
think often a degree or so lower than the air temperature though in
clear conditions, as they are radiating heat directly out into space. So
if the car owners are covering their cars with tarpaulins, they may have
a point.
--
John Hall "Hard work often pays off after time, but laziness always
pays off now." Anon