Dark Sky's forecasts, maps and embeds will keep working on the web until July 1st. The website will stay online after then "in support of API and iOS App customers." As for the API, it'll remain active until the end of next year, but Dark Sky won't let anyone else sign up.
"Our goal has always been to provide the world with the best weather information possible, to help as many people as we can stay dry and safe, and to do so in a way that respects your privacy," the Dark Sky team wrote in a blog post. "There is no better place to accomplish these goals than at Apple. We're thrilled to have the opportunity to reach far more people, with far more impact, than we ever could alone."
It seems likely Apple will use Dark Sky's know how to bolster its own Weather app. Apple has used data from Yahoo (which is owned by Engadget's parent company Verizon) and The Weather Channel to power the app over the years.