It's time to start building the app. Create a new blank Xamarin.Forms app using .NET Standard as the Code Sharing Strategy, and select iOS, Android, and Windows (UWP) as the platforms. We will name the project Weather.
As the data source for this app, we will use an external weather API. This project will use OpenWeatherMap, a service that offers a couple of free APIs. You can find this service at https://openweathermap.org/api. We will use the service called 5 day / 3 hour forecast in this project, which provides a five-day forecast in three-hour intervals. To use the OpenWeather API, we have to create an account to get an API key. If you don't want to create an API key, we can mock the data instead.