The problem is that when I coded this, I took the lazy way of declaring the function inside the snippet. As such, when you call the snippet twice, it tries to declare the function twice, which PHP finds unacceptable.
Backup your current version and try the version I just attached. Upload the include file to assets/snippets/WeatherX, and paste the new WeatherX.php in as your snippet. If icons weren’t working, upload the "graphics" folder, as well.
Although this snippet works easier out of the box, it is really deprecated in favor of FeedX.
http://modxcms.com/forums/index.php/topic,12657.0.html
FeedX is essentially an XML parser that is super easy to template. As such, you can access weather provided by Yahoo, Weather.com, or Wunderground.
http://modxcms.com/forums/index.php/topic,12657.0.html
It already has default presets/templates for Wunderground and Weather.com, and I attached a template for Yahoo.com (
http://cmssandbox.com/MODx095/index.php?id=57). Read through that entire thread, it is very informative. Also it provides the possibility of doing multiple days (
http://cmssandbox.com/MODx095/index.php?id=83) and many other neat things.