Pipes start to freeze when temperatures hold around 20°F, but an exposed or uninsulated pipe — a hose bib, a crawlspace run, a pipe in an exterior wall — can freeze at higher temperatures and in as little as 3 to 6 hours. Enter tonight's forecast low and where the pipe is to gauge your risk and get the right prevention steps, or switch to the second tab if a pipe is already frozen. In the Pacific Northwest the danger spikes during arctic-outflow cold snaps; how Bellevue pipes freeze and burst in those events is covered in our frozen and burst pipes in the Pacific Northwest guide, and active emergencies go to our emergency plumbing in Bellevue line.
Enter the forecast low and pipe location to see the freeze risk.
Risk thresholds follow the ~20°F “temperature alert” standard (sources below); wind and exposure can freeze pipes at higher temperatures. This is guidance, not a guarantee.
The temperature alert threshold for freezing pipes is about 20°F — the point where unprotected pipes begin to freeze, according to the Building Research Council. Exposed or uninsulated pipes can freeze at higher temperatures (25–32°F), and wind makes it worse.
At 20°F or below, an unprotected exposed pipe can freeze in as little as 3 to 6 hours; insulated interior pipes take longer. Between 20°F and 32°F, pipes can still freeze with prolonged exposure of roughly 12 hours or more. The pipe's location matters as much as the number — a pipe in a heated interior wall is far safer at 22°F than a hose bib or a crawlspace line at the same temperature.
This is why the calculator above asks where the pipe is: the same forecast low is low-risk for one pipe and high-risk for another. In the Pacific Northwest, the real danger is the occasional arctic-outflow snap where temperatures sit below freezing for multiple days — that's when Bellevue sees its burst-pipe surge.
Let a thin stream of water drip from the farthest faucet, open cabinet doors on exterior walls, keep the heat steady day and night, and insulate exposed pipes and hose bibs. Disconnect garden hoses before the first hard freeze.
Moving water resists freezing, so a pencil-thin drip from the faucet farthest from the meter keeps water moving through the most vulnerable run. Opening under-sink cabinets lets household heat reach pipes on exterior walls. Foam pipe sleeves and heat tape protect exposed garage, crawlspace, and outdoor pipes — the ones most likely to freeze on the Eastside.
Because PNW cold snaps arrive only a few times a year, many homes have pipes that were never properly insulated for them. Insulating the exposed runs once, before winter, is far cheaper than a single burst-pipe cleanup.
If a pipe is frozen but intact, open the faucet it feeds and gently warm the pipe from the faucet end with a hair dryer or hot towels — never an open flame. If it has burst and water is spreading, shut off the main immediately and call for emergency help.
Keep the faucet open while thawing so melting water can escape and relieve pressure. Work from the faucet toward the frozen section so the thawed water has somewhere to go. Know where your main shutoff is before you start — a frozen pipe sometimes reveals a split only once it thaws and water rushes out. If you can't reach the pipe, it won't thaw, or you see a crack, shut the water off and call a plumber.
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Serial-number formats are decoded from published manufacturer and inspection references. Always confirm against the date on your unit's rating plate.
Around 20°F is the widely-cited 'temperature alert threshold' where unprotected pipes begin to freeze. But exposed or uninsulated pipes — hose bibs, crawlspace runs, pipes in exterior walls — can freeze at 25–32°F, and within 3–6 hours when it's that cold. A pipe's location matters as much as the temperature, which is why the calculator above factors in both.
An unprotected exposed pipe can freeze in 3 to 6 hours once temperatures drop to about 20°F. Better-protected interior pipes take longer, and in the 20–32°F range it usually takes around 12 hours of sustained cold. Prolonged Pacific Northwest cold snaps that last multiple days are when the risk is highest.
Yes — letting a pencil-thin stream drip from the faucet farthest from your water meter keeps water moving through the most vulnerable pipes, and moving water resists freezing. Combine it with opening under-sink cabinets on exterior walls and keeping your heat steady overnight during a cold snap.
Open the faucet that pipe feeds, then gently warm the frozen section from the faucet end using a hair dryer, heat lamp, or hot-water-soaked towels — never an open flame or torch. Locate your main shutoff in case the pipe split and gushes when it thaws. If you can't reach it, it won't thaw, or you see a crack, shut off the water and call a plumber.
