Wanted to share how I made a "decently" realistic thunder and lightning prop. It's not very cheap, but worth it as it lasts forever.
First and foremost, to make it realistic, unlike most of the strobe/sound gadgets you can buy for like $20 or more, you want the lightning to come first, then the thunder sound. And like the real world, not all lightning flashes are the same intensity and they vary how many flash before the thunder is heard.
So, first, I bought a Chauvet strobe controller. I forget how much I paid, I think like $30 or so, maybe a bit less. They still sell it on there site. CH-751 is the model I have.. might have a new one now. Basically this controller offers a timer mode, a sound activated mode, and a pulse mode. The pulse mode allows you to fire off the signals as often as you like. We'll use the sound activated mode as I'll explain below. The strobe light I bought, Chauvet ST-200 is no longer sold by them... and as mine works I haven't bothered to check to find another strobe that takes the 1/4" mono plug that my strobe controller uses. I am sure there are others out there. The unit I have easily lights up my garage very brightly, and from outside you can see it pretty nicely across the street. Again, I forget the price, but I think it was around $50 or so.
So, using the audio trigger mode of the strobe controller, what I do is set up a stereo audio file, one channel is the actual thunder sound that I play on a speaker outside, the other channel is where I put the strobe activating sound, and I play that on another speaker far away from any sound. With the strobe controller on sound mode, any near by sounds can activate it as well, so I set the sensitivity to "low" and play the speaker pretty loudly right next to it.. so that distant sounds wont trigger the strobe.
Now, to make it somewhat realistic... I want to trigger the lightning BEFORE the thunder.. so in my stereo audio track, I place a quick burst of sound (anything that can trigger the strobe is fine... can be you shouting, a drum sound, whatever) where I want to activate the strobe. Anywhere from immediately to a few seconds later, I have the thunder sound on the other channel. But... to be a wee bit more realistic, I sometimes put a couple flashes together, some back to back, some a 1/4 second or so apart. That gives the impression of two or three flashes before thunder is heard. Usually for "distant" thunder, I flash once, and for close/loud thunder, I put two flashes close together and the thunder right after it so it sounds as if the storm is right on top of you.
That's about it. For the most part, this isn't too difficult to set up, and it does a pretty decent job of looking and sounded like real thunder and lightning. You can easily mix in rain in the background if you wanted.. I prefer to not do that as I play some songs too from a different set of speakers.
"What about using DMX?"... I honestly thought.. DMX would be the best way to go for a good overall "scene". Here's the thing. Until this year, I had no DMX capable devices. I almost bought a DMX strobe light.. but it didn't have a non-DMX trigger method.. and it would mean I would have to run a DMX controller of some sort, be it my computer or a standalone controller. Ultimately, I want to head in that direction.. but I am slowly building up my halloween gear each year as money is tight, and also don't really have the space to put stuff right now. But, if I could use DMX.. the best thing about it with strobes is that you can really simulate intensities.. so you can have short not so bright flashes, then some brighter ones with closer/louder thunder... that would be the best! Until then.. the way I have done it seems to work pretty well with the only "unrealistic" part being that the flashes are all the same brightness. Now.. supposing you have the desire to do so.. you could hook up a few outside lights, even some inside lights, to simulate a storm messing with your electrical power of the house.. so with a few DMX channels, flash a few other lights around the house on and off to make it seem as if there is electrical interference.. now that would be the best!
Anyway, I am sure there may be cheaper alternatives to this.. I have yet to find a decent realistic all-in-one sound/lightning box that is more realistic than what I do.. but maybe there is.
Hope ya'll enjoy.