For reasons I don't fully understand, this doesn't always work properly in the val.town preview, however if you use the endpoint in a browser it should be fine.
Wunderground stationId are ALL CAPS.
https://croniac-wundergroundstationdisplayv2.web.val.run
https://esm.town/v/Croniac/WundergroundStationDisplayV2
<script type="module" src="https://esm.town/v/Croniac/WundergroundStationDisplayV2" />