FrostList

When to Winterize Sprinklers in Arvada, CO

ON TRACK95 days until first 28°F freezeOct 14

In a typical year, winterize your sprinkler system in Arvada by October 4. The median first 28°F hard freeze at Arvada's NOAA station is October 14 (1991–2020 normals); one year in ten it arrives as early as September 28. At about 5,398 feet, valley cold can run a few degrees ahead of the station reading.

OUTLOOK

Typical first first 28°F freeze near Oct 14; local deadline about Oct 4. The live 10-day outlook loads here.

Local freeze dates for Arvada

ThresholdEarly (1-in-10)MedianLate (9-in-10)
32°F (light freeze)Sep 20Oct 5Oct 18
28°F (hard freeze)Sep 28Oct 14Oct 26
24°F (severe)Oct 8Oct 24Nov 7

NOAA station: Wheat Ridge 2 · 2.5 mi away · 5,398 ft elevation.

Arvada draws its numbers from Wheat Ridge 2, 5,398 feet up and 2.5 miles away. Its median first-freeze dates are 32°F by Oct 5, 28°F by Oct 14, 24°F by Oct 24. That hard freeze has landed anywhere from Sep 28 to Oct 26, a swing of roughly 28 days. Spring's last 32°F freeze clears around May 5. Snowfall averages 76 inches a year, first reaching an inch near September.

In Arvada, freezing nights (32°F) typically begin around Oct 5 and the first hard freeze (28°F) follows near Oct 14. The 32°F date swings from Sep 20 at its earliest to Oct 18 at its latest, near 28 days. The last spring freeze averages May 5 and as late as May 18, which sets the safe window for reopening outdoor water and de-winterizing gear. Roughly 76 inches of snow fall in an average year, so a clear roof edge and a running snow blower matter as much as the freeze itself.

Your sprinklers checklist

  1. Shut off the irrigation water supply at the main valve and, if you have one, the dedicated sprinkler shutoff inside the house.
  2. Turn off the controller or set it to the "rain" mode so valves do not open while the system is dry.
  3. Drain the mainline using the manual, automatic, or blow-out method your system was built for; most pros prefer a blow-out.
  4. Connect a compressor to the blow-out port through a proper adapter and run 40–80 psi, one zone at a time, until the heads mist and clear.
    Helpful gear: Air compressor blow-out adapter — Recommended pick
  5. Insulate the backflow preventer and any above-ground valves; this brass assembly is usually the first part to crack.
    Helpful gear: Insulated backflow preventer cover — Recommended pick
  6. Cap outdoor hose bibs with foam covers after the hoses come off so the last exposed fittings stay protected.
    Helpful gear: Foam outdoor faucet covers — Recommended pick
  7. Open the backflow test cocks a quarter turn so any trapped water has room to expand.
  8. Log the date and the psi you used; you will want the reference next fall.

What to have on hand

Air compressor blow-out adapter
Quick-connect fitting that mates a shop compressor to your irrigation line.
Recommended pick
Insulated backflow preventer cover
Pouch that shields the above-ground backflow valve from early frost.
Recommended pick
Foam outdoor faucet covers
Slip-on domes that protect hose bibs after you drain them.
Recommended pick
Portable air compressor
A modest pancake unit moves enough air to clear most home zones.
Recommended pick

What this means locally

Compared with nearby cities, Arvada's first-freeze date near Oct 14 sits about a week ahead of Westminster (Oct 21) and about a week ahead of Denver (Oct 21). Colorado's deadlines span Sep 30 to Oct 23 statewide — one date for all of Colorado would be off by weeks for Arvada. Once you know Arvada's freeze date, use it to protect your indoor pipes and winterize an RV if you own one too.

Other winter jobs in Arvada

Every task below is dated to Arvada's own freeze and snow normals.

Frozen pipes → Sep 20Ice dams → Aug 16Car battery → Oct 14Snow blower → Aug 25Sump pump → May 5RV → Oct 4Boat → Oct 7Motorcycle → Oct 5

See the full Arvada winter checklist, in order →

Frequently asked questions

What temperature freezes sprinkler pipes?
Standing water in shallow lines and the backflow assembly can start to freeze once air temperatures drop into the mid-20s for several hours. Buried mains are slower, but the exposed brass backflow preventer and above-ground valves are the parts that crack first, which is why the deadline is tied to the first 28°F freeze, not the first frost.
Do I need to blow out my sprinklers or just drain them?
It depends on how the system was installed. Manual or automatic drains work if the lines were pitched to low points. Most irrigation pros recommend a compressed-air blow-out because it clears water that drains miss, especially in flat yards. If you are unsure how your system drains, a blow-out is the safer choice.
What happens if I don't winterize my sprinkler system?
Water left in the lines expands as it freezes and can split the backflow preventer, crack valves, or break fittings. Repairs to a backflow assembly commonly run more than the cost of a blow-out. The damage often is not visible until you turn the system on in spring and find leaks.
How much does a sprinkler blowout cost?
A professional blow-out typically costs somewhere in the range of a modest service call, depending on the number of zones and your region. Buying an adapter and using your own compressor costs less over time, but you need enough air volume to clear each zone. Prices rise once the first freeze warnings appear, so book early.
When should I turn my sprinklers back on in Arvada?
Wait until the last spring freeze has passed, which averages around May 5 here in the 1991–2020 normals. Turning the system on too early risks refreezing a charged line. Open the main slowly to avoid a pressure surge, then walk each zone to check for winter damage before you rely on the schedule.
Can I winterize sprinklers myself?
Draining and insulating are within reach for most homeowners. A blow-out is doable if you own a compressor that moves enough air and you use a proper adapter, working one zone at a time at safe pressure. If your system lacks a clear blow-out port or you are not confident, hiring a pro once is a reasonable call.

Data: NOAA 1991–2020 normals via Wheat Ridge 2, live outlook by Open-Meteo. Sources · Methodology. Last updated: July 11, 2026.