Download both the Conky script and the Helvetica at the link below:
http://gnome-look.org/content/show.php/ConkyWeather%2BClock?content=133251
sudo apt-add-repository ppa:conkyhardcore/ppa
sudo apt-get update && sudo apt-get install conkyforecast
cp /usr/share/conkyforecast/conkyForecast.config ~/.conkyForecast.config
In-order to make use of ConkyForecast you will need to nab a XOAP Code @ http://www.weather.com/services/xmloap.html and enter it in the .conkyForecast.config file, now neatly copied into your home folder, along with your location code which can be found sitting at the end of a URL search for your location @ weather.com
run
conky -c ~/weather+clock/conkyrc