iOS Home Screen Widgets that were introduced in iOS 14 are automatically updated by iOS within a 15-30 minute interval. The widgets then download measurement data of your netatmo weather station from the netatmo data server and update their content.

The update interval is calculated randomly and is always between 15 and 30 minutes. If a widget is not updated for a long time, then there is either a problem with the netatmo data server or the data could not be updated due to device-specific problems. See this FAQ for possible solutions.