OpenWeatherMap has a rather strict limit on the usage of their weather data source:
You should only request one forecast per 10 minutes of usage.
Week Weather lets you try to fetch new forecasts more frequently but displays a warning then. Requesting forecasts too often can result in inaccurate or faulty data.
While OpenWeatherMap works fine most of the time, we experienced occasional periods with slow response times and / or data issues. These issues are usually resolved a couple of hours later, so please be patient if such issues arise. You can also temporarily switch to yr.no as data source at any time.