Im wondering how I can add blueprint-system to the sun that comes with the scene, when you start a new scene, so you can make a day/night system.
I also want to have dynamic-skies so I can have a time-line for various sky-opacity + thunder, rain and so forth. So, is it possible to make a “all-in-one” weather system?
I had a look at : Greg's Blog: UE4 Time of Day Setup, but havent tried it out yet, so I dont mess up something if I start on a weather-system
Who cares if you mess it up? You can always start over. Get that time of day system, put it in a new project and build your weather system on top of it. There are different approaches for rain; you can either make intersecting planes that cover the whole game area and have panning raindrops or you can make a particle system that follows the player.
I trying to follow tutorial: Unreal Engine 4: Day night cycle using Blueprint. - YouTube . I got it to work, but I have no such options in the timeline, where he sets the values on the keys, so the sun rotates way faster than on the tutorial. I followed it step-by-step. I only have “Time” and “Value”. Did change on 4.3?
I dont know how that system works, never used it really. But you can get more help from it’s thread here:
Thanks, I will have a look 
Yes that project comes highly recommended from me, I have been going through it all and it is just great. Make sure you download the version listed on the last page, it will have day/night cycles with moon & sun. The moon still needs to be animated, but that won’t be too difficult.
It looks great, they did an awesome job putting it together, and made the blueprints nice, clean, and compartmentalized.
And after you get it working in your scene, the same scene is getting better performance with the old skybox deleted, and the new one added in its place. Then you just need to hook up the directional lights and it works!
Try it out! will be a lot of fun to tinker with in the next few days. 
Im a big fan of dynamic gameplay myself. Do you think its possible to add options for storms?
Possible? for sure! I created a new project recently, where I do nothing but tinker/tweak/hack/break/and hopefully fix
There are many ways to do weather, from Volumetric clouds down to more simple plane’s with a semi-transparent cloud shapes drawn as materials onto them, it depends a lot on how close to the user the effect is being displayed.
Another was is to download various “SkyBox” images, but that still doesn’t make thicker clouds, just changes the look of the sky.
There are more ways to go about , I am also working on currently using BP’s, Dynamic and animated materials, and particles for rain. It is not ready for prime time yet, but I will let you know when I have something worth sharing!
Im want to use a dynamic-weather blueprintsystem on the sun that comes with the example_map when you start a new project. Have you done som progress?
im looking through the time of day working on a blueprint for my weather system atm hope someone comes up with some nice tips