Try just putting the weather info in without the $if statements; if there's no connection, it just won't display anything, AFAIK.
Hm. Unless you've got some hard coded info in your template, like "Temp:"...Mine doesn't have anything hard-coded, so if, for example, my Conky loads before my WLAN comes up, it just doesn't display anything for weather. Have a go and see what it comes up with.
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