Speaking of temperature ratings, by now i got quite a few of them doing stuff like being cameras or being an exit node for a network of sensors in unheated places.
No problems were observed during the winter, with temps as low as -30*C (CPUs on Pis never got below zero, however).
So it's not like it's going to die once water freezes over, especially for hobby uses.
Getting back on the broader topic, the whole stack of 10 RPi zeros had been chipped apart and used in a variety of projects.
The most persistent one is a time lapse/network camera, of which i made a bunch, and which are placed in many locations within 2000 km radius.
Another one is an IoT gateway, since i like making all kinds of smart home thingies but don't feel like it's a good idea to connect them to the internet. So they are all wired together, and there is also a Pi zero in there somewhere with a wifi dongle that does the encryption and communications with the outside world.
These projects revealed more flaws of the Pi, more precisely that it's flakey.
The cameras tended to lock up every week or so, for reasons i never figured out (in all climates).
There is a watchdog timer in the CPU, but it does not work all that well.
In the end i had to add timed reboots to them, and an external reboot timer for the ones that would need a plane trip to access.
Annoying.
The other thing is that the CPU does not do real time tasks all that well - i wrote a kernel module to handle the wired bus i mentioned, and it never quite worked right. Best i can tell is that the timers onboard got some randomness to them, or there is some kind of not-controllable frequency changing going on.
Annoying.
In the end, it's not as in-control as you can get on a proper microcontroller, which is largely offset by it's ability to do microcontroller level things while carrying a full scale Linux.