Cleaning the raw text file to get only the temperature column with awk, something like: awk '{print $10}' output.log > celcius.log was the second step.
And finally a small gnuplot script to fetch the celcius.log file which contained only 2 digits by row:
45
43
44
40
45
40
.
.
.
Gnuplot script to generate a png file:
set term png
set output "celcius.png"
set ylabel "C"
set xtic auto
plot "celcius.log"
And the final result:
