The only proof that it rained teeth is Shelby's word. We can rule out that it was anything non-supernatural like the hillbillies or some natural phenomenon, otherwise she would have had teeth to pick up off the ground to prove it to some one.
They only need to explain it if it definitely happened, and we do'nt know that it definitely happened for sure.

In the promo for episode 8, someone (I think Monet) is grabbing for a tool from a table and next to one of the tools is what looks like a bunch of teeth. So, it may be explained next week.

We know the woods beep with people's perceptions. It could have been actual hail and she saw teeth.

When did that happen in the show, I can't seem to remember? Also, cool video - I live in Nova Scotia oooOOOoooOOOooo

The point was dramatic license.
Not every little detail is going to be explained, especially in something this meta.
It was a tv show engineered for ratings and shock value fictionalized to tell a story within a story via a reenactment.
As much as I like things explained, this is one time where we don't really need an explanation.
No Quarter

Maybe so, but come on they wouldn't have shown it just because its an actual phenomenon. There was a point to showing it just like their was a point to showing the raining teeth.
TWIN PEAKSBATES MOTELAHS**HANNIBALHUMANS*MR ROBOT

Heaving Ground is an actual phenomenon. Nothing supernatural about it.:
Dude, its Beacon Hills.

Thats true. And i guess the ground heaving up like it was breathing was part of the embellishments in the reenactments also.
TWIN PEAKSBATES MOTELAHS**HANNIBALHUMANS*MR ROBOT

We don't know it ever rained teeth. We were watching a re-enactment of a made up story for all we know.

Maybe it was a hallucinationcaused by the spirits in the place.
I'm thinking Shelby might be a little unstable.