More and more themes offer you a weather viewer from the springboard or lockscreen.
The only problem is that the themes are often settled on the city of its creator. Here is a small tutorial for those who do not know how to adapt these themes according to their city.
An integrated theme with weather.
IFile or log-in SSH
Find the file type setting and type of weather code
Explore your theme or SSH iFile to find the setup file of the theme. This one is named by the creator of the theme, so you'll have to look a bit location of this file in the theme. Its name is most often "settings" or "config" in xml (but it's different on each topic)
In these files, there are often other settings such as language, time format, etc ... it's up to you to customize these settings to your tastes.
Once you locate the file, open it and find the part about the weather and the associated code
Example iFile and the new theme "Heavy Metal HD"for iPhone 4