TSV

​Sure. They manually set exposure and WB at the beginning and then let the camera run.

It's kind of a daring concept to expect from viewers to watch this in real time. Nothing unexpected happens, it's like watching paint dry. But I hope you are not determined to repeat this. 

​You have to experiment. Your GH4 may allow you to set exposure times of 1/15 s (or so). Because you don't actually have a shutter. Motion rendition, of course, would be poor, you'd have effectively 15fps within 30fps (or 12 within 24). You could also combine time lapse (looong exposure times) and rain, something quite unusual. I saw an experimental short film at a festival a few months ago, where the filmmaker showed a busy highway first, then cranked down fps gradually by simultaneously prolonging exposure times. First the cars became ghostly trails, then they disappeared altogether. If you follow any rules how to make the perfect time lapse, the result will be perfectly boring. If you find your own way to do it, it will be interesting ...

​There are so many possibilities to depict rain. You should find out what rain means to you, personally. A force of nature, a romantic-melancholic mood, an abstract layer/pattern that filters the colors and shades, whatever. You could use sDoF to accentuate individual foreground drops, dripping from a roof or running down a pane. You could use absolute DoF and wide angle lenses to show how the rain decreases contrast in the distance (whereas it increases contrast in the foreground). You could counteract (or not) washed-out colors. You could show dramatic clouds or a perfectly white sky. You could make it look like fog by longer exposure times. Or, on the contrary, you could surrealistically change the rain's direction by very short exposure times (captures individual drops occasionally, which sometimes can make it look as though they were rising). Sound adds a lot to how rain feels. See Tarkowsky's films (i.e. Andrej Rubljev, spelling not checked). In short: Make up your mind about what you want to show.

I never made time lapse shots of sunrises/sunsets. Because I felt many had put so much effort in this, and I surely coulnd't top their results. If I needed to, I wouldn't do it as everybody else would do it. Why show the sun at all? Why not only the wandering shadows? Why must there be a smooth fade-in/fade-out or a seemingly evenly lit clip? When the first strong rays appear, why shouldn't my scene not be (slightly) overexposed? Isn't that what makes a sunrise interesting? You know, as beautiful as they might be, nobody likes sunrise-time lapses. Because they tend to look the same whereever they're taken. Make something special. Astonish us.

As for rain I only tried once. Since my gear(sony nex-5r) is not weather proof and I only had a 50mm lens and 3 m² to move around I had to go for close-ups. I think close-ups for rain work quite well but I would like to see some landscape shoots since 4k will definitely show more rain drops in air:)

 

I'm not exactly sure what you're looking for regarding the rain scenario. Your GH4 should be pretty weather resistant so you shouldn't have to worry about a little rain, but personally I would use that camera cover in an all out down pour just to be safe.

It is my understanding that you should definitely use Auto (no flash) mode for time-lapse. But why not try a few time-lapses before June? Put 'er in auto and film the sunrise and set from your current location. You'll be a pro by the time you take your trip.