What Temperature Do Pipes Freeze? And How Long It Takes
Updated October 2026 · 5 min read
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Quick answer: water freezes at 32°F, but pipes inside a home usually aren’t at serious risk until the outside temperature drops to about 20°F or lower for several hours. That figure, the “temperature alert threshold”, comes from field research by the University of Illinois Building Research Council on uninsulated pipes in unheated spaces. Pipes in attics, crawl spaces, garages and along outside walls can freeze sooner, especially in wind.
Pipe freezing temperatures at a glance
| Outside temperature | Risk to your pipes |
|---|---|
| 32°F (0°C) | Water can freeze, but pipes in heated parts of the house are generally safe. Outdoor hoses and faucets are at risk. |
| Around 28°F (−2°C) for several hours | A hard freeze. Exposed pipes and pipes in unheated spaces start to be at risk. |
| 20°F (−7°C) or lower | The alert threshold. Uninsulated pipes in attics, crawl spaces and outside walls are likely to freeze, and burst pipes become common. |
Warmer states are often more at risk during a rare hard freeze. Homes there often have pipes in attics or exterior walls with little insulation, because freezing weather isn’t expected.
How long does it take pipes to freeze?
Exposed pipes often start to freeze after about 6 to 8 hours at 20°F or below. Wind, drafts through gaps in walls, and pipes with no insulation speed this up. Pipes in heated rooms can go much longer. So an overnight hard freeze is the classic time for pipes to freeze, and they often burst the next morning as they start to thaw.
Will my pipes freeze if the heat is on at 65°F?
Usually not the pipes in heated rooms. But pipes in unheated spaces (crawl spaces, garages, attics) or inside cold exterior walls can still freeze in a severe cold snap even with the heat on. That’s why opening sink cabinets and letting a faucet drip matters on very cold nights.
What temperature should I keep my house to stop pipes freezing?
Keep the thermostat at the same temperature day and night during a cold snap. If you’re going away, the American Red Cross recommends leaving the heat on and set no lower than 55°F. See its guide to preventing frozen pipes.
Will shutting off the water keep pipes from freezing?
Shutting off the water doesn’t stop the water already in the pipes from freezing. But if you shut off the main valve and drain the lines by opening the faucets, there’s little water left to freeze and much less pressure. That’s the best protection for a home that will be empty and unheated. Learn where your main shut-off valve is.
How to protect your pipes when temperatures drop
Based on American Red Cross guidance:
- Let cold water drip from faucets on exposed pipes when it’s very cold.
- Open kitchen and bathroom cabinet doors so warm air reaches the pipes.
- Keep the garage door closed if water lines run through the garage.
- Disconnect and drain garden hoses, and close the inside valve to outdoor faucets.
- Insulate pipes in attics, crawl spaces and garages with pipe sleeves or UL-listed heat cable.
- Seal gaps where cables or pipes come through outside walls, because drafts speed freezing.
Signs your pipes have frozen
- Only a trickle, or nothing, comes out of a faucet.
- Frost on an exposed pipe.
- A toilet that won’t refill.
If you see these, act quickly. Read what to do about frozen pipes. If a pipe has already split, follow our burst pipe steps.
Pipe frozen and you can’t reach it, or it’s inside a wall? Don’t wait for it to burst. Call a plumber: +1 (877) 270-1778
Frequently asked questions
Do pipes freeze at 32 degrees?
The water in them can, but pipes inside a heated home rarely freeze at 32°F. The risk rises sharply as temperatures approach 20°F, especially for pipes in unheated or uninsulated spaces.
What is considered a hard freeze?
Generally, temperatures of about 28°F or lower for several hours. That’s cold enough to damage plants and to start putting exposed pipes at risk.
How long can a house go without heat before pipes freeze?
It depends on how cold it is outside and how well the house is insulated. In a well-insulated house, it can take a day or more for the inside to get cold enough. In a cold snap near 20°F or below, pipes in exposed spots can freeze within several hours. If the heat goes out in freezing weather, shut off the main water and drain the lines.
Related guides
- Frozen pipes: what to do now and when to call a plumber
- Burst pipe? What to do right now
- Main water shut-off valve: where it is and how to turn it off
Source for the 20°F threshold: Freezing and Bursting Pipes (City of Paola, citing the University of Illinois Building Research Council).
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