Its rare, but on occasion, the weather widget may not display on the mobile app after the creation of an Event or Event Brand which is a really simple fix! 

Within the Event Brand, created for an event, you will find Advanced Options. Start by clicking on the Actions button on the Event Brand and click on Change Theme:

Scroll to the bottom of the General page and click on Advanced Options. Here you will find options that will apply to the Mobile App and the roles that users will play within the app. The App option will be dependant and will vary but the Default Role will always be Mobile App User

Once the App and Role has been corrected, the weather widget will then display the correct information for your event.