"Alan Gould" wrote in message
...
In article , Franz Heymann notfranz.
writes

I thought air frost occurs when the temperature of the air falls below
zero
and ground frost occurs when the temperature of the soil falls below
zero.

Neither air nor soil become frozen at zero temperature. Frost is frozen
particles of moisture in the air or on the ground.

I don't go by air frost/ground frost. I go by car frost, ie when you have to
scrape it off the windscreens. First one today :-((

Steve