The name in the titlebar is "mise-à-jour" ; it should be "mise à jour" (without tirets). Moreover, some words are not translated at all, like "rain showers" ("averses") or "partly clouded" ("légèrement nuageux"). (OS : Mageia 3 beta 2 DVD 64 bits)
Please report errors in translations to the xfce i18n mailing list (https://mail.xfce.org/mailman/listinfo/) or - even better - directly to the appropriate translation team for your language (see http://translations.xfce.org/). You could also join that team and help to improve the weather translation file (and maybe those of other applications you use) by contributing. This bug tracker is mainly for bugs in applications, I doubt translators will get noticed here. Besides, the errors might have been fixed already, though only in the git repository and therefore only for future versions.
Thanks, I'll do this.