Not with MCreator's existing tools. You'd need custom code.
...Which is to say you could make a custom global event, but it'd be difficult to control the appearance of the sky and whatnot. There may be a plugin for this, otherwise I'd recommend seeing if you can find similar projects with a GitHub repository that you could study. (To get an idea of what classes you're dealing with. Not to shamelessly plagarize.)
Not with MCreator's existing tools. You'd need custom code.
...Which is to say you could make a custom global event, but it'd be difficult to control the appearance of the sky and whatnot. There may be a plugin for this, otherwise I'd recommend seeing if you can find similar projects with a GitHub repository that you could study. (To get an idea of what classes you're dealing with. Not to shamelessly plagarize.)