How to Winterize Your Home in Denver: Sprinkler Blowouts, Tree Care and the Sidewalk Snow Rule

What should you do to get a South Denver home ready for winter?

Blow out your sprinklers before the first hard freeze (Denver averages its first freeze around October 7), give trees a deep drink on dry days above 40 degrees, clean gutters after the leaves drop, service the furnace, test for radon, and plan to clear your sidewalk by the day after every snow. A notice and a $150 fine can follow if you do not.

If you want to winterize your home in Denver without paying for a burst pipe or a dead maple next spring, October is the month to start. This guide is written for homeowners in South Denver, from the brick bungalows of Washington Park and Platt Park to the ranches of University Hills and Hampden, and it sticks to the local details that national checklists miss: our early and unpredictable freezes, our dry winter air, the radon in Colorado soil, and the city’s rule for shoveling sidewalks.

None of this takes a contractor’s budget. Most of it is a weekend of chores spread across October and November, plus one or two calls to book a sprinkler blowout or a furnace check before everyone else does.

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When does winter really start in Denver?

Earlier than many newcomers expect, and with less warning. According to the National Weather Service office in Boulder, the average date of Denver’s first freeze is October 7, and the average date of the first measurable snowfall is October 19. The earliest first freeze on record came on September 8, 2020, and the latest held off until November 15, 1944. Denver averages 56.9 inches of snow a season.

What makes Denver tricky is the swing. A week of 70 degree afternoons can end with a single night in the low 20s, and that one night is enough to crack a sprinkler pipe or a backflow preventer that still holds water. The safe approach is to treat the first week of October as the start of freeze season, even if the forecast looks mild.

Blow out your sprinklers before the first hard freeze

Water left in irrigation lines expands when it freezes, and the damage often does not show until you turn the system back on in spring. Colorado State University Extension’s PlantTalk guidance lays out the basics: shut off the water supply to the system and empty the lines. Some systems have manual or automatic drain valves, but over the years lines can sag and form low spots that still hold water, so many homes need a blowout with compressed air.

CSU Extension recommends a professional with the right air compressor for the job. A homeowner can do it, but too much air pressure, or water left behind, can damage heads, valves and pipe. Sprinkler companies across the metro area book up quickly once the first cold snap hits the news, so call in late September or early October and ask for a slot before mid October.

Two local tips:

Protect the backflow preventer. In many South Denver yards it sits above ground near the house. CSU Extension suggests insulating it, wrapping the insulation in plastic, and carrying it down to the pipes at ground level, secured with duct tape. That can let you keep watering a little longer during a warm fall.
Do not forget the outdoor faucets. Disconnect garden hoses, drain them, and close the indoor shutoff valve for each outdoor spigot if your home has one. Older homes in neighborhoods like Bonnie Brae often have spigots without frost protection.

Give your trees a drink before and during winter

South Denver’s big shade trees are a large part of what makes these neighborhoods feel the way they do, and they lose water all winter in our dry, windy air. Denver Water’s guidance is simple: water trees and shrubs during dry spells, when there has been no significant moisture for about three weeks, and only on days when it is above 40 degrees and there is no snow on the ground. Frozen soil cannot absorb water, so water early enough in the day for it to soak in.

How much? Denver Water suggests about 10 gallons for each inch of trunk diameter, measured near the base, and 5 to 18 gallons for shrubs depending on their size. A slow soaker hose or a hose on a trickle, moved around the drip line of the tree, works better than a quick spray at the trunk. Once your sprinklers are blown out, a hose and a bucket do the job.

A few more habits that help trees through winter:

Spread two to four inches of wood mulch over the root zone, keeping it a few inches away from the trunk.
Rake leaves off the lawn so they do not mat down and smother the grass, then use them as mulch in beds.
Knock heavy, wet snow off branches gently with a broom after spring and fall storms, when trees still carry leaves and break more easily.
For large pruning jobs, hire a certified arborist, and check with Denver Forestry before any work on trees in the strip between the sidewalk and the street.

Clean gutters and point downspouts away from the house

Many South Denver streets are lined with mature trees that hold their leaves into late October, so plan to clean gutters after most of the leaves are down rather than in September. Clogged gutters overflow during wet fall snows, and the water soaks the soil right against your foundation.

Make sure every downspout empties at least a few feet from the house, using an extension or a splash block. This matters most in older homes with basements, which describes a lot of the housing stock in Washington Park, Platt Park and Bonnie Brae. If you own one of these older homes, our look at historic bungalows in Washington Park covers what to watch for in a house of that age.

While you are on the ladder, look at the roof. Missing shingles, cracked flashing around chimneys, and gaps where critters can get into the attic are all easier to fix in October than in January.

Service the furnace and get ready for dry air

Schedule a furnace inspection and cleaning before the first truly cold night, change the filter, and plan to check it again every month or two through the heating season. If your home has a boiler or radiators, as many older South Denver homes do, have those checked too.

Test your carbon monoxide alarms and smoke alarms, and replace any that are past the date printed on the back. Every home with a gas furnace, gas water heater, gas stove or attached garage should have working carbon monoxide alarms near the bedrooms.

Denver’s winter air is very dry, and forced air heat makes it drier. A whole house humidifier on the furnace, or a portable one in bedrooms, can help with dry skin, static and cracking wood floors and trim. Clean humidifiers regularly so they do not grow mold.

Test for radon while the windows are closed

Radon is a colorless, odorless gas that seeps up from the soil, and Colorado has a lot of it. The Colorado Department of Public Health and Environment calls radon the leading cause of lung cancer among nonsmokers in the United States and estimates about 500 lung cancer deaths a year in Colorado. In January 2026, the department estimated that about half of Colorado homes have radon levels above the EPA’s action level of 4 picocuries per liter.

Winter is a good time to test, because the house is closed up and the result reflects the air you breathe most of the year. Short term test kits are inexpensive at hardware stores, and the state has offered free test kits while supplies last; check the CDPHE radon page for what is available now. If your result is high, a certified mitigation contractor can install a system that vents the gas from under the house. CDPHE also runs a Low Income Radon Mitigation Assistance program for qualifying homeowners.

Know Denver’s rule for shoveling sidewalks

This is the one item on the list that comes with a fine. As reported by Denver7 and 9News, Denver expects homeowners to clear the sidewalks in front of and beside their homes by the day after the snow stops, and businesses to clear theirs as soon as it stops. If a sidewalk is not cleared, a city inspector can leave a notice. Residents then have 24 hours, and businesses four hours, before a recheck and a possible $150 fine.

If you see a sidewalk still covered 24 hours after a storm, you can report it to the city by calling 311. Rules can change, so confirm the current details on denvergov.org or with 311 before the first storm.

Denver’s Snow Angels program matches volunteers with older residents and people with disabilities who need help clearing their walks. You can reach it at snowangels@denvergov.org or by calling 720 913 7669. It is also a great way to help a neighbor if you have a shovel and a free morning.

Before the first storm, put a good shovel and a bag of ice melt by the front door. Ice melt labeled safe for concrete and pets is worth the extra cost, especially on newer sidewalks and steps.

A simple October and November checklist for South Denver homeowners

Late September or early October: book your sprinkler blowout and furnace service.
First week of October: disconnect and drain garden hoses and close indoor shutoffs for outdoor faucets.
Before mid October: blow out the sprinkler system and insulate the backflow preventer.
October: water trees and shrubs deeply before the ground freezes, then mulch the root zones.
Late October or early November: clean gutters after the leaves drop and extend downspouts.
November: change the furnace filter, test carbon monoxide and smoke alarms, and set up humidifiers.
November through January: run a radon test with the house closed up.
All winter: shovel sidewalks by the day after each snow, and water trees on dry days above 40 degrees.

If you are new to owning a home here, our first time home buyer guide to South Denver covers the bigger picture, from neighborhoods to budgets.

Frequently Asked Questions

When should I blow out my sprinklers in Denver?

Aim to have your sprinkler system blown out before mid October. The National Weather Service puts Denver’s average first freeze on October 7, and it has come as early as September 8, so booking a blowout in late September or the first days of October is the safest plan.

How much should I water my trees in winter in Denver?

Denver Water suggests about 10 gallons of water for each inch of trunk diameter, and 5 to 18 gallons for shrubs. Water only when it is above 40 degrees with no snow on the ground, and only after about three weeks without significant moisture.

How long do I have to shovel my sidewalk in Denver?

Homeowners are expected to clear their sidewalks by the day after the snow stops. If an inspector leaves a notice, a home has 24 hours and a business four hours before a recheck, and a $150 fine can follow if the walk is still not clear.

Do South Denver homes really need a radon test?

Yes. The Colorado Department of Public Health and Environment estimates that about half of Colorado homes are above the EPA’s action level of 4 picocuries per liter, and the only way to know about your house is to test it. Winter, with the windows closed, is a good time.

Who can help an older neighbor shovel their sidewalk?

Denver’s Snow Angels program pairs volunteers with older residents and people with disabilities. Email snowangels@denvergov.org or call 720 913 7669 to ask for help or to volunteer.

Sources

South Denver Guide Team