WorkWindow

Concrete Pouring Weather in Seattle, WA: 10-Day Windows & Best Months

In Seattle, the label math works from April through October: that's the stretch with 8+ workable days a month against typical concrete pouring rules. The single best month is July, averaging 27 days that clear every check — highs of 77°F, lows near 58°F, and a 13% daily rain chance. The strip above runs Seattle's live forecast; the table below ranks all 12 months.

GOOD — clears every rule MARGINAL — exactly one soft miss NO — a hard fail, or two soft

The rules this check uses

Every verdict above applies this table to Seattle's hours. DIY scope only: the freeze row outranks everything, and structural work belongs to engineer/ACI specifications.

Typical label thresholds for concrete pouring — the ruleset behind every Seattle verdict above.
CheckThresholdWhy it matters
Air temperature 40–90°F — ideal 50–85°F Checked across the working day, 8 a.m.–6 p.m., against Seattle's hourly forecast — not just the daily high.
Overnight low ≥40°F during the first 48 h The engine reads every overnight hour in the cure window, not just Seattle's forecast low.
Dry before no soaking (≥1.0") in the prior 24 h Rain before the pour only matters if the ground is soaked or standing in water.
Dry after <0.1" rain for 6 h after (12 h light rain after finishing still risks surface marks) A downpour in the first 6 hours can wash the surface; after final set, rain actually helps curing.
Wind ≤20 mph (rapid surface drying up to 28 mph) Wind wrecks application first (drift, lap marks) and carries debris into wet work second.

Always follow your product label — formulas vary. These rows are the industry-typical range; the can in your Seattle garage is the contract.

Best months for concrete pouring in Seattle

Workable days in Seattle, WA: days meeting the temperature rules, discounted by NOAA rain odds — a 1991–2020 estimate, not a forecast.
MonthAvg highAvg lowRain odds/dayWorkable days 
January 49°F 37°F 60% 0
February 51°F 37°F 56% 0
March 55°F 39°F 56% 5
April 60°F 44°F 49% 15
May 66°F 49°F 38% 19
June 71°F 54°F 27% 22
July 77°F 58°F 13% 27
August 77°F 58°F 14% 27
September 72°F 54°F 28% 22
October 61°F 46°F 47% 16
November 53°F 40°F 58% 6
December 48°F 36°F 60% 0

Figure 159 workable days a year in Seattle, spread across April through October. Shoulder months turn on the overnight rule: an afternoon at 60°F passes, but the 40°F night floor is what actually opens the season in April. For the statewide picture, the Washington page compares peak months city by city.

The rain odds swing hard across the year — 13% of days in July up to 60% in December. Season the plan accordingly: prep in the wet months, apply in the dry ones.

Sealing the same driveway later? Sealcoating in Seattle wants warmer nights (50°F+) than the pour did.

Numbers above come from NOAA's 1991–2020 normals for Seattle Boeing Fld, Wa Us, 8.4 km from the city center — close enough that neighborhood microclimates (shade lines, river valleys, urban heat) matter more than station distance. See how these day counts are scored.

Seattle by the numbers

Prep checklist

  1. Clear the 48-hour rule first: two nights over 40°F. April opens that door in Seattle; December (36°F average lows) slams it.
  2. Set the stage first: forms braced, subgrade compacted and lightly damp, every tool within reach, help confirmed.
  3. Cut plastic sheeting and weight it at the pour's edge — Seattle sees rain on 13% of July days, and the 6-hour rule doesn't negotiate.
  4. Keep the mix stiff (oatmeal, not soup) — every extra quart of water is permanent surface strength lost.
  5. Screed while it sheens, float when the sheen dulls, and never trowel bleed water back in.
  6. Edge and joint with an edger + float set — control joints every 2–3 slab-thicknesses in feet.
  7. Hold the moisture in (sheeting or misting); when October nights dip toward 46°F, a curing blanket is the difference.
  8. Feet after 24–48 h, cars after about a week — and structural work follows engineer/ACI specs, not this list.

Gear that saves a window

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FAQ

What temperature is too cold to pour concrete?

The line is a 40°F low inside the first 48 hours; an actual freeze (32°F) physically damages young concrete. Seattle's December nights average 36°F — firmly out — while July nights hold near 58°F. Small pours only; structural work follows engineer/ACI specs.

Can you pour concrete before rain?

The engine wants 6 protected hours; light rain later actually feeds the cure. With 60% rain-day odds in December versus 13% in July, Seattle's dry-season pours barely think about this rule and wet-season pours live by the radar. For small DIY pours; structural schedules follow ACI.

How long does concrete need to be protected from freezing?

Keep it above freezing for at least the first 48 hours (the engine calls any sub-40°F low in that window a NO). In Seattle that rules out roughly December-adjacent months entirely and makes shoulder-season pours a two-night forecast decision. DIY scope; anything structural follows engineer/ACI cold-weather practice.

Is it OK to pour concrete in hot weather?

To a 90°F high, yes — with shade, cool mix water, a damp subgrade, and a dawn start. Above 90°F the surface sets while the core is plastic and shrinkage cracks map the slab. Seattle averages 0 such days in July — rarely the binding constraint here.

How long before you can drive on new concrete?

A week before tires, 24–48 hours before feet — at July-typical Seattle temperatures (77°F highs). When nights slide toward 36°F, add days: cure speed is temperature. Early loads print permanent marks; the bag's cure table wins every argument.

Best season for concrete work in Seattle?

April through october — the months with 40°F+ nights, sub-90°F days, and manageable rain. July leads at 27 workable days; December bottoms out near 0.

Other projects in Seattle

Concrete Pouring nearby

Guides

Climatology: NOAA 1991–2020 normals via SEATTLE BOEING FLD, WA US (8.4 km from Seattle center, elevation 20 ft); live outlook by Open-Meteo.