The info updates well from the NWS and it's a great component. I would recommend, but don't use the module on every page. Just use it on one "Weather" page.
Thanks for the review. The slowness is caused when the component retreives new weather data from the National Weather Service server. The optional cronjob feature was recently released for version 6 of Z Weather, which updates the weather data instead of your website visitors. This will improve your website performance on pages where the Z Weather component or module are used.