My kitty snores something fierce, too. I'm pretty sure she would've been coyote food by now if she were an outside kitty, too. I use white noise as a solution. The vet doesn't think that there is anything wrong with her that is causing the snoring. Sometimes when she is asleep in the daytime I hear it. Of course, this kitty has allergies, so that could be part of her problem. She has some of the same allergies I do. I don't think humidifiers would be the answer for us, because we have the opposite problem. I have a measuring device for the humidity level in here, so I know that isn't the issue for us. If you heard the way this cat snores, you might bust out laughing yourself. You wouldn't be able to help it.
One of my boys snores so loud, if he was an outside kitty, I'm sure he would be some wild animal's dinner. But, I had him checked and he is also healthy.
I've had cats that snored. One was really bad. I took him to the vet but there was nothing wrong. If it worries you, I'd take him in just to be sure. But it's probably nothing.