Is it too late to blow out my sprinklers in Colorado?

Past September 22, Colorado is into the window where a hard freeze can arrive at any time, so do it now rather than waiting for a better weekend — but if a hard freeze has already been through, do not pressurise the system to check it. Drain what you can, leave it off for the winter, and inspect for damage at spring startup instead.

When is the first frost in Colorado?

The long-term normal for the first 32°F freeze in Colorado is around October 4, with a normal early year arriving by September 22. A light frost will not usually reach buried pipe — it is a sustained hard freeze, several hours below about 28°F, that does — but an exposed backflow preventer is vulnerable well before that. For calendar context, that median ranks 6th of the 45 state pages we publish dates for.

What does it cost to winterize a sprinkler system in Colorado?

A professional blow-out in Colorado typically runs $50–250 depending on zone count. Freeze repairs typically run $170–$2,500+, with the backflow preventer the priciest common casualty. If you are doing it yourself, stay at or below 50 PSI.

When can I turn the sprinklers back on in Colorado?

The last spring freeze in Colorado normally passes around May 6, but that is a median — half of years freeze later than it. Give it a couple of weeks of margin and treat May 18 as the earliest safe date, later if the forecast is still marginal. Re-pressurise slowly, a quarter turn at a time. All told, the system sits out roughly 31 weeks of the year here.

Sprinkler winterization dates

When to Winterize Sprinklers in Colorado

Winterizing is a deadline problem, and the deadline is local. In Colorado the first freeze of the autumn normally arrives around October 4, which puts the blow-out window at roughly September 6–22 — start about four weeks out and be finished by September 22. Colorado's deadline is not the average date, it is the early edge of it: a normal early year freezes by September 22, and the backflow preventer sitting above ground outside your house in Colorado is damaged by the first real freeze rather than the tenth.

Winterize between: September 6–22
Average first freeze: October 4; An early year: September 22
Turn it back on after: May 18; Median last freeze May 6, plus a margin — half of years freeze later than the median.

A statewide date has to work for the coldest part of the state, so this is anchored to the earliest-freezing NOAA station we track here rather than to an average — which means it is deliberately early for milder areas. Find your own city below if it is listed for a closer date, and let the forecast have the final say.

That caveat is the ceiling for a static page. YardLedger watches the live forecast for your address instead, and warns you when a hard freeze is actually about to reach Colorado. Get my freeze reminder

Anchored to the earliest-freezing of these NOAA stations, not averaged across them: Colorado Springs, Denver.

The window against the freeze band

Blow-out window — September 6–22
First-freeze band — from September 22
Median first freeze — October 4

Drawn from Colorado's own NOAA freeze normals. The green window ends where the amber band begins: September 22 is the early edge of a normal freeze year, which is the date to be finished by.

Why September 6–22, and not later

A median is not a deadline

Half of Colorado's years freeze earlier than October 4, and a normal early year gets there by September 22. Scheduling the work to finish on the average date means missing it every other year.

The backflow device goes first

Buried pipe has soil buying it time. The backflow preventer is brass, above ground and full, so around Colorado it can be damaged by the first real freeze rather than the tenth — and it is the most expensive part on the system.

Contractors book out

If you are hiring it out, the few weeks before the first freeze are the busiest of the irrigation year in Colorado. Booking at the start of the window rather than the end is the difference between a date you chose and one you were given.

When is your first freeze?

The dates above are Colorado's normals. Your yard's can differ — enter your ZIP for the NOAA station nearest you, rather than the one anchoring Colorado. Free, no signup required.

Your ZIP code

Free · no signup · NOAA 1991–2020 normals

How Colorado compares

The statewide date is set by Colorado Springs, the earliest-freezing of the 2 stations we track in Colorado. Denver, at the other end, normally holds out until October 6 — a 2-day spread hiding inside one "statewide" number. That number has to be honest for the cold end of the spread, which is why the window above will read early if you are in the Denver half of the state.

Of the 45 state pages we publish, Colorado comes due 6th — between Wyoming and Montana on the calendar. Montana shares Colorado's statewide median — a climate coincidence; each envelope is built from its own stations. Statewide, Colorado's envelope spans about 214 days of freeze season (October 4 to May 6), more than half the year — and the spring restart is keyed to the latest spring freeze among the same stations, so startup clears the whole state rather than just its mildest corner.

The closer answers: Colorado Springs (October 4), Denver (October 6). Each was measured at its own NOAA station, so pick the metro nearest you over the statewide number — and if none of them is close, split the difference toward the earlier date, not the later one.

What to do inside that window

The field sequence, numbered as the full winterization guide numbers it — each step opens its full detail there, including which method suits your system.

Professional blow-out

$50–250

If you skip it

$170–$2,500+

DIY pressure ceiling

50 PSI

What it costs, in detail · No compressor? · Draining the backflow preventer

Frequently asked questions

When should I winterize my sprinkler system in Colorado?: Between about September 6–22, finishing by September 22. The average first fall freeze in Colorado is around October 4, but a normal early year arrives by September 22 — so that early edge, not the average, is the deadline. A statewide date has to work for the coldest part of the state, so this is anchored to the earliest-freezing NOAA station we track here rather than to an average — which means it is deliberately early for milder areas. Find your own city below if it is listed for a closer date, and let the forecast have the final say.
Is it too late to blow out my sprinklers in Colorado?: Past September 22, Colorado is into the window where a hard freeze can arrive at any time, so do it now rather than waiting for a better weekend — but if a hard freeze has already been through, do not pressurise the system to check it. Drain what you can, leave it off for the winter, and inspect for damage at spring startup instead.
When is the first frost in Colorado?: The long-term normal for the first 32°F freeze in Colorado is around October 4, with a normal early year arriving by September 22. A light frost will not usually reach buried pipe — it is a sustained hard freeze, several hours below about 28°F, that does — but an exposed backflow preventer is vulnerable well before that. For calendar context, that median ranks 6th of the 45 state pages we publish dates for.
What does it cost to winterize a sprinkler system in Colorado?: A professional blow-out in Colorado typically runs $50–250 depending on zone count. Freeze repairs typically run $170–$2,500+, with the backflow preventer the priciest common casualty. If you are doing it yourself, stay at or below 50 PSI.
When can I turn the sprinklers back on in Colorado?: The last spring freeze in Colorado normally passes around May 6, but that is a median — half of years freeze later than it. Give it a couple of weeks of margin and treat May 18 as the earliest safe date, later if the forecast is still marginal. Re-pressurise slowly, a quarter turn at a time. All told, the system sits out roughly 31 weeks of the year here.