Will Pipes Freeze in Boulder County, CO? 86 nights a Year
Freeze nights in Boulder County
In a normal year Boulder County, CO gets 86 nights at or below 20°F, the point where bare pipes in a garage, attic or outside wall start to freeze. That is more than 85% of US counties.
Risk level: Severe. The risk season runs October to May, worst in December.
It depends where the pipe is
| Pipe | Freezes near | Nights a year |
|---|---|---|
| Outdoor spigot, open crawlspace | 32°F | 200 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 86 nights |
| Insulated pipe in unheated space | 10°F | 35 nights |
| Inside the heated house | 0°F | 10 nights |
Foam-sleeving a bare pipe in unheated space takes it from 86 nights of risk to 35 nights. A 12 ft heat-tape kit runs $17 to $37; an average burst-pipe repair is about $500.
Month by month
Nights at or below 20°F in a normal year.
First 32°F night is usually around 09/23, last around 05/24. For 20°F: 10/24 to 04/21.
How cold Boulder County nights get
Average winter (Dec-Feb) low: 16°F; the coldest month, January, averages 16°F overnight. 10 months normally bring at least one night below 32°F (Jan, Feb, Mar, Apr, May, Jun, Sep, Oct, Nov, Dec). Nights below 10°F, cold enough to freeze insulated pipe in an unheated space, come in January, February, March, April, October, November, December: 35 nights a year, and 10 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 16°F | 16°F | 21°F | 25°F | 34°F | 42°F | 48°F | 46°F | 39°F | 30°F | 22°F | 16°F |
Boulder County next to its neighbours
Gilpin County, CO, 28 km southwest, gets 126 nights below 20°F to Boulder County's 86 nights. Broomfield County, CO, 33 km southeast, gets 58 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Boulder County, CO | - | 200 nights | 86 nights | 16°F |
| Gilpin County, CO | 28 km southwest | 235 nights | 126 nights | 13°F |
| Broomfield County, CO | 33 km southeast | 150 nights | 58 nights | 19°F |
| Clear Creek County, CO | 51 km southwest | 234 nights | 136 nights | 12°F |
| Denver County, CO | 58 km southeast | 156 nights | 61 nights | 18°F |
| Jefferson County, CO | 59 km south | 208 nights | 105 nights | 14°F |
| Grand County, CO | 61 km west | 265 nights | 154 nights | 2°F |
Boulder County within CO
Boulder County ranks 38 of 64 CO counties for nights below 20°F. The most is Summit County, CO at 177 nights, with a 5°F average winter low. The fewest is Mesa County, CO: 44 nights, winter lows near 21°F. At 8,161 ft, Boulder County sits 1,281 ft above the state's median county elevation of 6,880 ft.
What to do here
- Treat it as a building fix, not a night-of routine: insulate, heat tape, seal crawlspace vents.
- An automatic leak shutoff pays for itself if one burst is avoided.
- Know where the main shutoff is before the first hard freeze.
The dates to be done by: when freeze season starts and ends.
Where this comes from
NOAA 1991-2020 climate normals, blended from 3 nearby stations and adjusted for elevation; closest is Gross Rsvr, CO, 18 km away (close match). A normal year, not tonight's forecast: check the forecast low for the night itself. Why elevation is part of the blend: how county numbers are made.