Paul,
There is a daily graph of minute by minute depression of grass min below air
min at Wokingham on this page:
http://www.woksat.info/wwp6.html
Scroll down the page and you will see a list of daily Graphs. Scroll down
that page and you will see a graph of grass level temp and grass-air
difference. The difference trace is grey, and is on the right hand scale.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.woksat.info/wwp.html
or
www.btinternet.com/~wokingham.weather/wwp.html
"Paul Hyett" wrote in message
...
What would be a ball-park figure for the average difference between it &
the screen minimum value?
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)