Is it too late to blow out my sprinklers in Seattle, WA?

Past November 9, Seattle, WA 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 Seattle, WA?

The long-term normal for the first 32°F freeze in Seattle, WA is around November 21, with a normal early year arriving by November 9. 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 61st of the 63 metros we publish dates for.

What does it cost to winterize a sprinkler system in Seattle, WA?

A professional blow-out in Seattle, WA 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 Seattle, WA?

The last spring freeze in Seattle, WA normally passes around March 8, but that is a median — half of years freeze later than it. Give it a couple of weeks of margin and treat March 20 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 15 weeks of the year here.

Sprinkler winterization dates

When to Winterize Sprinklers in Seattle, WA

Winterizing is a deadline problem, and the deadline is local. In Seattle, WA the first freeze of the autumn normally arrives around November 21, which puts the blow-out window at roughly October 24 – November 9 — start about four weeks out and be finished by November 9. Seattle, WA's deadline is not the average date, it is the early edge of it: a normal early year freezes by November 9, and the backflow preventer sitting above ground outside your house in Seattle, WA is damaged by the first real freeze rather than the tenth.

Winterize between: October 24 – November 9
Average first freeze: November 21; An early year: November 9
Turn it back on after: March 20; Median last freeze March 8, plus a margin — half of years freeze later than the median.

This is the long-term NOAA normal for the nearest first-order station, so it describes a typical year rather than this one. Elevation, cold-air drainage and how built-up your street is all move the real date at your address — watch the forecast as the window opens, and act on the first hard freeze in it rather than on the date.

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 Seattle, WA. Get my freeze reminder

From the long-term NOAA freeze normals for Seattle.

The window against the freeze band

Blow-out window — October 24 – November 9
First-freeze band — from November 9
Median first freeze — November 21

Drawn from Seattle, WA's own NOAA freeze normals. The green window ends where the amber band begins: November 9 is the early edge of a normal freeze year, which is the date to be finished by.

Why October 24 – November 9, and not later

A median is not a deadline

Half of Seattle, WA's years freeze earlier than November 21, and a normal early year gets there by November 9. 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 Seattle, WA 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 Seattle, WA. 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 Seattle, WA's normals. Your yard's can differ — enter your ZIP for the NOAA station nearest you, rather than the one anchoring Seattle, WA. Free, no signup required.

Your ZIP code

Free · no signup · NOAA 1991–2020 normals

How Seattle, WA compares

Of the 63 metros we publish winterization dates for, Seattle holds the 61st-earliest median first freeze — 59 typically freeze sooner, 2 hold out longer, and Seattle lands 27 days behind the middle of that list. Atlanta, GA lands on the very same median as Seattle — a coincidence of climate, not shared data; each metro is measured at its own NOAA station. The closest published dates on either side of Seattle belong to Atlanta, GA (November 21) and Dallas, TX (November 25) — winterization advice written for either transfers here almost unchanged, which is not true of a national average.

Between the median first freeze (November 21) and the median last spring freeze (March 8), Seattle's freeze season runs about 107 days — call it 15 weeks with the system down, under five months — a comparatively short winter. That arithmetic is behind both ends of this page: the blow-out window is the fall edge of it, and the spring-startup date is the other, pushed past Seattle's median because half of years freeze later still — leaving roughly 258 days of running season between startup and the next blow-out.

Within Washington, Spokane typically freezes 45 days earlier (October 7). If your address sits nearer one of those metros, its page is the better anchor. The statewide page, by design, follows the earliest of them rather than the average.

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 Seattle, WA?: Between about October 24 – November 9, finishing by November 9. The average first fall freeze in Seattle, WA is around November 21, but a normal early year arrives by November 9 — so that early edge, not the average, is the deadline. This is the long-term NOAA normal for the nearest first-order station, so it describes a typical year rather than this one. Elevation, cold-air drainage and how built-up your street is all move the real date at your address — watch the forecast as the window opens, and act on the first hard freeze in it rather than on the date.
Is it too late to blow out my sprinklers in Seattle, WA?: Past November 9, Seattle, WA 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 Seattle, WA?: The long-term normal for the first 32°F freeze in Seattle, WA is around November 21, with a normal early year arriving by November 9. 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 61st of the 63 metros we publish dates for.
What does it cost to winterize a sprinkler system in Seattle, WA?: A professional blow-out in Seattle, WA 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 Seattle, WA?: The last spring freeze in Seattle, WA normally passes around March 8, but that is a median — half of years freeze later than it. Give it a couple of weeks of margin and treat March 20 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 15 weeks of the year here.