I’m a noob at MS, but since I need something like this eventually, I tried the following. It seems to work though I didn’t play much with it.
I ignored the modulation, but this might give you a starting point.
Drizzle goes in a wave variable
Thunder Claps go in an array of Waves
To create the delayed variables, pull off the On Nearly finished of the wave players, then grab those variables and drop them while holding the Alt key
Play with the randomization parameters for better randomization
If you want to feed the waves from BP, make them Inputs rather than Variables
What the randomizing attempts to do, is between 1 and 10 seconds, select a thunderclap from the 0 to 2 array of thunderclaps. The delayed variables are triggering both the drizzle and the thunderclaps.
If someone sees an error please speak up.
Sorry about the modulation, I only had a couple of minutes free to do this. It also doesn’t have gain but that should be an Input float the BP gives it so your overall player selectable ambient sound volume and master can adjust it.
Edit: I had a moment to mess around with the Modulator Node. If you are using just the pitch randomization, use a Random Float node feeding into the Pitch Shift of the wave players. These would be triggered by the same output trigger playing the waves. If you are using the Modulator Volume shift, this could be done a Random Float node too, but be sure the volume can’t result in a value greater than the player specified ambient volume control.
Edit 2: I was working on a different metasound, but it needed the modulator’s two functions in it. This photo below is not the weather system (it is for playing one-shot spatial/attenuated sounds), but note the sections I’ve marked in red. Those are the pitch and volume randomization needed also for a weather system to vary the pitch on each call and vary the volume as a Modulator node would have done in the Sound Cue. Again, this screen shot is not the weather system, just showing the nodes needed for that functionality. I will eventually do a weather system including that and to allow for weather changes controlled by blueprint. If interested I will post them.
Make note that the Volume Randomization goes prior to clamping the final gain. This would be necessary in the Weather manager too.