Apple in iOS 17 has introduced a number of changes across its stock apps, including the Weather app. With the update, there are some minor changes to the functionality and design of the app.
The biggest update is an option to see yesterday's weather in the 10-day forecast. In iOS 16, you can only view the current day and the next 10 days, but in iOS 17, you can view current day, the next 10 days, and the weather from the previous day.
10-day forecasts show the chance of rain each day and offer a "daily summary" instead of a forecast.
The main Weather interface has been updated with large "My Location" text for the weather forecast in at your current location, with the city underneath. In iOS 16, it simply said the city, which could be confusing when navigating through multiple saved cities.
Some of the weather modules have been relocated, with rain and hourly forecasts shown first. News and alerts are shown lower in the app, and there is a new "Averages" weather module that displays how the current temperature deviates from the historical average on that day.
Apple does not appear to have made any changes to the data that is used for the Weather app, despite complaints of its inaccuracy following the incorporation of the Dark Sky app.
Source: Macrumors