1. Go to the weather page by tapping on one of the weather forecast icons in either the main calendar app or widget. Alternatively use the drop down menu for switching calendar views and tap on the weather image at the top of the hamburger menu:
2. Tap on the banner at the bottom promoting the premium weather subscription.
3. A small pop-up from Google Play Store should now appear asking you to subscribe to the premium weather forecast for EUR/USD 2.50 per year. First time users get a free 14-day trial before the credit card is charged. You may cancel the subscription any time during this period.
If you do not have a creditcard, you can also use paypal to pay for your purchase.
5. Confirm your purchase by inserting your password for your Google account that's linked to the Google Play Store.
6. Congratulations, you've now got access to the premium weather features!
7. You should also receive an email from Google Play Store confirming your subscription.
Please note that there is a standard 14 days trial, so if you changed your mind, you can always cancel the subscription within 14 days.