How does getting thirsty in the World Beyond work?

How does it work? I think that it only affects you when you're moving, but how much do you have to move to get thirsty? Is it luck-based? Does it matter the time of day?

It seems like whether it's day or night matters, but I'm not sure. In my first town, I went out into and came back from the World Beyond in the day and I got thirsty, but in my current town I went out in the night, scavenged all day, and came back in in the night and I didn't get thirsty. Does moving at night really make you get thirsty faster, or is it just luck/me remembering wrong?

Any other info on how getting thirsty works would be appreciated too.

I just tested it, and it indeed takes 11 squares to become thirsty. I would suppose its another 11 squares before you get dehydrated as well.

It is a set amount. I haven't experienced it myself, but I believe you get thirsty after moving 10 squares.