Weather apps are a popular learning project, and most entries here are built around a public forecast API. SwiftLanguageWeather and YoCelsius are the most starred and focus on design and animation. Tropos, from thoughtbot, and OSS Weather both have App Store links. Oscar Weather uses Open-Meteo, and Sky Wizard adds animated forecasts and 3D models.
Several apps were built on the Dark Sky or Weather Underground APIs, which have since shut down, so they will not fetch data without changes. Sol, RainMan and Pocket Forecast are marked as unmaintained. If you are building your own, compare how projects handle location permission, caching and API keys. Open-Meteo needs no key for non-commercial use, which makes those apps easier to run.