Is it normal for rear windshield to break on its own????

Anything is possible, suggest you get a security camera/game camera.

 

Never came across forum comments about Prius windows shattering on their own. With the "other" events going on, security camera or giant dog on looong leash might be in order.

 

I always blame my ex

 

Hmmmm.....
You don't have a Fuelly siggie at the bottom of your post, so you might not be one of "those" Prius drivers who like to serve as a rolling impediment to normal traffic flow.
What this means is that I've never seen automotive glass shatter without a little help.
Sometimes, the "help" hard to isolate.
I've seem glass shatter from lawnmowers, road rocks (yes...even the rear) even falling bullets....... because some people have this weird idea that rifle rounds can reach escape velocity.
Weather can do it.
Aaaaaaaand let's face it....
You're in the Republic of Texas.

Sometimes?
It's not random.
If lots of things are happening to your car you may need to take stock of your driving and employ some security measures.
People who aren't wired to spec will often lash out at things that piss them off.
There are a lot of signs in Texas that say: "Drive friendly - the Texas way." which always used to baffle me until I had to drive there more regularly.
The "Don't Mess With Texas" signs are more apt, but were meant as an anti-pollution message rather than a statement of policy towards other drivers.

Take a look at how you drive, and where you live....if you've ended a relationship badly....or have political stickers on your Bumper.
Houston can be rough in some spots.

Game cameras are cheap.

 

Looking at the picture, it doesn't seem to have been hit. I get the sense some stress built up, where it's bonded along that edge, causing it to break??

 

It's not the type of damage that would be caused by someone with bad intent (although, of course, anything is possible).

Mendel's comment makes most sense.

Is this a vehicle you purchased new, in 2004?

Tires, meh, I have personally experienced, as well have read other accounts that the wheels of the Prius can lend themselves to lost air more than others. If your tires are slashed or the valve stems pulled, that's a different dog.

Seems like a string of bad luck.

Police. If you are extremely lucky, they might send someone to take a report, or tell you to come in to make one. Odds are, even in my low-crime area, they will nicely tell you to screw off.

 

I've seen several posted here during my tenure on PC. But this does seem to be quite infrequent.

I did witness it once, in 100 degree temperatures in a climate where that is uncommon.

 

It's extremely unlikely for glass to break on its own. If it had a crack, the cold weather will often cause cracks to creep further, but I've never seen a windshield break like that from cold weather. To me it looks like your car was hit by an object in the lower left corner.

It doesn't look like it was a malicious attack on your windshield as this would be an unlikely place to hit it, if that were the intent. More likely is something like a kid with a baseball who hit it there accidentally.

 

It's fairly common for sunroofs to do this. I don't see why the rear glass in the hatch would be any different. Could have just been weather and I'd try to just chalk it up to that rather than stress over it.

 

Try this salvage yard. It's in Houston.

 

The glass may have already had a chip or small crack in it which is cause it to break on its own at some point.

I had an oil change done to my car and by the time it was done my front windshield was broken. Luckly the car shop repaired it for free.

Another time i drove 100 miles and watched a small crack on the front windshield grow in size by over 12 inches during the trip.

 

welcome! be glad it's not a prime.

 

Broken by road debris? Insurance will pay

 

In the middle 1960s my father was working from an office in Denver but very frequently visiting a preproduction facility on the western slope. He reported having the rear window fracture on a rental car twice. On both occasions it was extremely cold and the window shattered shortly after he crested a ridge when the cold soaked window was suddenly hit by sunlight.

This particular mechanism seems not likely in the case at hand, and it well may be that modern automotive window glass differs in some important way, but I thought I'd mention it as a case of not quite spontaneous window fracture.

 

I still think that this is anthropogenic.
We had a Prius in a larger town suffer a broken rear hatch glass shortly after I responded to this thread.
As a matter of fact, it looked very much like the OPs picture.

Ours wasn't a case of "Prius Hate" but rather it was a disgruntled customer....or a bored teenager.
The indicator was a large rock that was found in the cargo bay.