Forum GraphWeather

Hi all,
I'm looking for more templates to draw graphs with PHP. Now I use the standard PHP template for GraphWeather, that I modified to work with WeatherLink db exported to MySQL.

Unfortunately if I plot graphs in log time period, the view is not very good.
I instead see very interesting graph such this:

http://meteo.rouen.free.fr/stat.html

Do you have any hints or code for long term (monthly, yearly) graphs?

Thank you very much
Best Regards
marco