Homeowners, how cold does it have to get before you worry about your pipes freezing?

Not a homeowner, but wouldn't that vary based on how well insulated your home and your pipes are?

Yes.

When we lived in a trailer in Indiana, we started worrying around 10 F. When we moved into an older house, we worried about pipes along the exterior walls around 5 F. The year it got down to -20 F, we decided to move to Phoenix.

I've got water trickling even when it's above freezing. I'll get to it after football season.

When I lived in Madison, WI, it got down below 0 quite often (once to -40), and we never let the water run at night: I was there 5 years without a single freezup (as a renter, however). My ma, however, lives in rural NC, and if she doesn't let the pipes drip, she'll get 'em frozen if it gets down to around 20. She lives on a slab, by the way. I keep offering to pay to insulate her pipes, but she won't take me up on it.

We've been well below zero here and have never had a problem, but the only thing we have on exterior walls are a couple of outside faucets, and I always drain/shut those off before winter.

Water is a pretty inexpensive commodity, especially when compared to having a plumber come out to see ya on an emergency basis. Let a small steady stream flow in a sink furthest from the inlet to the house, or possibly at both ends of the house. This will keep water moving in the pipes and (most likely) prevent a freeze up. Where I live it's been -40 and we're on a municipal water system. The pipes in our 100 yr old home have never frozen. The ones beneath the road have however. Not a lot you can do about that sort of thing though. If there's a particular part of your house that gets frigid and there's exposed pipes about, place a small space heater there at the coldest of times.

Woha, I think we'd already put the heater up when it's 0 degrees Celcius. Which is about 35 Fahrenheit? I wouldn't, but my husband and parents say it's extremely important.

It's 32 F, pretty close!

I used to live out in the boonies (Blount County) and I have this very clear memory of my dad using a blowtorch to thaw our pipes out. Hardcore.

I've done that blowtorch to thaw pipes thing. Not fun. Was using a hairdryer at first, and then it was "oh, sod it..."

This was in an unheated commune. We had a couple of three-bar heaters that we used to leave on the pipes on a low setting over night when the weather got below about 20F. Leaving a drip in the kitchen didn't help - we'd wake up and it would be an icicle.

...until one day "Humphrey" decided to take the heaters to warm his room up while he slept. (You know, like he couldn't just chuck on a hat and some thermals like the rest of us.) Sodding pipes froze, but at least they didn't burst.

We had burst pipes in my parents house, in the summer palace wing of the house. First year we were there, we shut that wing off so we didn't have to heat it in the winter, but forgot to shut off and drain the pipes. Totally flooded the ballroom. Never made that mistake again.