Akram you may enjoy reading this. ; )
Here is a nice Q&q about frost, snow , has it ever snowed in san diego, how far south has it snowed in florida, what is the largest snowlake recorded, most snowfall amount.
Why water is sprayed on crops to protect from frezing temps.
How frost occurs on , why it occurs on some thing first.
Its a nice read for those interested.
Near bottom of page is where the talk is about dew point , air temp etc.
Here is link.
USATODAY.com