On 01/12/2020 10:36, John Hall wrote:
In message , Bernard Burton
writes
"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


I think the argument is that 0.0C is defined as the melting point of ice
rather than the freezing point of water.
Especially as water can stay unfrozen all the way down to -40