You did not say which version of the Portal you are using so I will assume 2.6.x. The weather portlet, and its page, are declared in the file jboss-portal.sar/samples/portal-weather-samples.war/WEB-INF/default-object.xml. As long as that file appears, each time you restart the app server the file will be read and the page and portlet created. Remove that file to keep them from reappearing.
Other *-object.xml files define the other pages and portlets. You can read more about the *-object.xml file in the Reference guide.
yep i'm using 2.6.4
Thanks for the tip Peter, got it :)