Pricing
Weatherling is a small app, so it has a small price. You buy it once from the Mac App Store and that is the end of the transaction.
What you get
The whole appEvery setting, every display, and the optional rain sound. Nothing is held back for a second purchase.
Every updateThe App Store keeps it current, and snow and sunlight arrive as updates to the app you already own.
No subscriptionNo renewal, no trial clock, and no in-app purchases. You pay once and it stays yours.
No accountNothing to sign up for. The app makes no network requests and collects no data.
Outside the US
$1.99 is the US price. Apple sets the equivalent price for every other storefront, including local taxes, so the App Store shows what you will actually pay before you confirm.
Try before you buy
There is no trial version, but the home page runs a live web version of the same idea, rain landing on and running down windows, so you can see whether it suits you before spending anything.
Refunds
Purchases are handled by Apple, so refunds are too. If Weatherling is not for you, request one at reportaproblem.apple.com. If something is broken rather than just not to your taste, the Support page is a faster route to getting it fixed.