Seattle rain is the single biggest thing working against your chimney. Sea-Tac's NOAA 1991-2020 normal is 40.34 inches of precipitation a year, spread across roughly 150 to 156 days with measurable rain. About 73 percent of that water falls between October and March, and November alone averages 6.31 inches. A chimney that stands above the roofline takes all of that on its crown, its mortar joints, its flashing, and its cap, and it never really dries out between storms from Halloween to spring break.
The short answer to "when should I take care of my chimney in Seattle?" is this: inspect and sweep in late summer or early fall before the wet season, fix anything that lets water in before November, and check for damage in spring once the rain eases. Below is the calendar we work from, with what to watch for in each stretch of the year and which jobs belong in which season. If you only remember one thing, remember that masonry repairs need dry weather to cure, so the window for most outdoor chimney work in Seattle runs roughly May through September.
Why rain hurts chimneys more in Puget Sound than almost anywhere
A brick chimney is not waterproof. Brick and mortar absorb water, and the Brick Industry Association's technical notes explain what happens next: when saturated masonry freezes, the water in the pores expands, and repeated freeze-thaw cycles cause cracking, spalling, and disintegration. Seattle does not get long hard freezes. Winter normal lows at Sea-Tac sit at 37.1 F in December and 37.7 F in January and February, and the city sees about 60 days a year where the temperature touches 32 F but only about 4 days that stay below freezing all day. That pattern is actually worse for wet masonry: the chimney soaks up rain, dips below freezing overnight, thaws by midday, and repeats. Building Science Corporation's freeze-thaw research on clay brick makes the same point from a different direction. The damage risk depends on saturation plus freezing, so keeping the masonry dry is what matters, not keeping it warm.
Add the housing stock and you see why leaks are so common here. Seattle's median home was built in 1976, Tacoma's in 1967, and Shoreline's in 1969. Many of those homes carry original brick chimneys with original crowns and flashing. Everett (median 1981) and Renton (median 1988) have more factory-built chimneys in framed chases, which fail in a different way: the galvanized chase cover rusts through and the wood chase rots from the top down.
The Seattle chimney calendar, month by month
January and February: watch and document
These are two of the three wettest months (January normal 5.78 inches) and the coldest, so this is when freeze-thaw damage actually happens and when leaks show up inside. Do not schedule masonry work now; mortar and crown material will not cure properly in 37-degree rain. Instead, pay attention. Look at the ceiling and wall around the chimney for new stains, check the firebox after a storm for standing water or damp soot, and notice any musty smell when the fireplace is cold. Take photos with dates. If water is actively coming in, call us. We can often tarp or seal the entry point as a stopgap and schedule the permanent chimney leak repair for drier weather.
March and April: the spring damage check
Rain drops from 4.17 inches in March to 3.18 in April, and the last frost in a typical year comes around March 24. Once the freeze-thaw crossings stop, what you see on the chimney is what you have for the year. From the ground, with binoculars if you have them, look for these signs:
- Brick faces that have popped off or flaked (spalling), and brick chips in the gutters or on the roof.
- White, chalky streaks on the brick (efflorescence), which the BIA notes as a sign of masonry taking on disproportionate water.
- Mortar joints that look recessed, sandy, or missing.
- Rust streaks running down siding or brick below a metal cap or chase cover.
- A crown with visible cracks, or chunks missing at the edge.
- Flashing that has lifted away from the brick, or a bead of old caulk that has split.
Please do not go up on the roof to check. Wet moss and a steep pitch are a bad combination, and a ladder inspection misses most of what matters anyway. We look at all of this as part of a chimney inspection, and the quote for any repair we find is free.
May through July: the repair window opens
May averages 1.88 inches of rain, June 1.45, and July only 0.60. This is the best stretch of the year for anything involving mortar, crown material, sealant, or new flashing, because the chimney is dry enough to bond to and the work has time to cure. Jobs that belong in this window:
- Crown repair or rebuild. The crown is the sloped slab on top of the chimney, and it takes the most direct rain of any surface on the house. A cracked crown lets water straight into the brick core. We repair sound crowns with a flexible coating and rebuild failed ones with proper overhang and slope. Crown rebuilds start at $299.
- Flashing repair or replacement. Flashing is the metal where the chimney meets the roof, and it is the most common leak point we find on 1960s and 70s homes. Re-sealing is a repair; corroded or wrongly installed flashing gets replaced.
- Chase cover replacement. On a framed chimney, a rusted cover is the leak. Replacement starts at $299.
- Chase rebuild. If the framing under the cover has rotted, the chase itself gets rebuilt, starting at $299.
Because summer is also when every chimney and roofing company is busy, booking in May gets you a better choice of dates than calling in August.
August and September: sweep and inspect before the season
August (0.97 inches) and September (1.61 inches) are still dry. This is when we recommend the annual sweep and inspection for wood-burning fireplaces. NFPA 211, the national standard for chimneys and fireplaces, recommends an annual inspection. Doing it now means any problem found inside the flue, such as a cracked tile liner, a damaged damper, or a bird nest from the spring, can still be handled before you want your first fire. Our sweep and inspection starts at $299, and it is also a convenient time to have a missing or damaged cap replaced, since the cap is what keeps the coming six months of rain out of the flue.
October: last call
October's normal jumps to 3.91 inches, so the window is closing. Small sealing jobs and cap or cover swaps can still be done on dry days, but larger masonry work becomes a gamble. If you know your chimney leaks and you have not had it fixed, October is the month to get us out for a free quote so the work can be scheduled on the first dry stretch, or at minimum so the entry point can be sealed before November.
November and December: the stress test
November is the wettest month of the year at 6.31 inches, and December follows at 5.72. November through January together average about 17.8 inches, roughly 44 percent of the annual total. This is when every flaw in the chimney shows up. If you did the summer repairs, this is the payoff: a dry firebox, no stains, and a fireplace you can use without worrying about what is happening above the ceiling. If you did not, this is when the stains appear. Note them, photograph them, and call. Same-day service is often available for active leaks.
What a Seattle chimney needs to stay dry
Every item on the calendar above comes back to four parts that keep water out. A sound crown with a drip edge sheds rain away from the brick. A cap keeps rain from falling straight down the flue, where it soaks the smoke shelf and mixes with soot into a corrosive sludge. Tight mortar joints keep the body of the chimney from soaking through; the BIA notes that improperly filled joints lead to leaky walls and to freeze-thaw cracking. And flashing closes the gap at the roof. When we inspect a chimney, we check all four and tell you which ones are actually letting water in, because a leak is not automatically the cap, and replacing the wrong part wastes money.
Tacoma, Everett, and the rest of Puget Sound
The calendar is the same across the region we serve, from Everett down to Tacoma and across the Narrows to Gig Harbor, because the rain pattern is the same. What changes is the chimney type. Tacoma and Shoreline lean heavily toward older brick masonry, so crown, mortar, and flashing problems dominate. Gig Harbor, Redmond, and Bothell have mostly 1990s and newer homes where factory-built chimneys and framed chases are the norm, so chase covers and chase rot are the usual culprits. Either way, the fix belongs in the dry months. See our Seattle service area page or the Tacoma page for details on where we work.
What to do next
- Right now, whatever the month, look at the ceiling and walls around the chimney and inside the firebox for water signs.
- If it is spring or summer, book a free inspection and quote so repairs land in the dry window.
- If it is late summer or fall, schedule the annual sweep and inspection before the first fire.
- If it is the wet season and water is coming in, call us at 206-453-2045. We will find the entry point, stop the water, and schedule the permanent fix.
Every quote is free, including a free second opinion if another company has already told you what you need. We price match and take 10 to 25 percent off on top of that, and if you are not happy with the work, we are not done.
Questions homeowners ask
What is the best time of year for chimney repair in Seattle?
May through September. Sea-Tac's normal rainfall drops to 1.88 inches in May and just 0.60 in July, which gives mortar, crown material, and sealants dry conditions to bond and cure. Most outdoor masonry work should be finished before October, when rain climbs back toward 4 inches a month.
When should I get my chimney swept in Seattle?
Late summer or early fall, before the first fire of the season. August and September are still dry, and an inspection then leaves time to fix anything found inside the flue. NFPA 211 recommends an annual inspection for chimneys in use.
Can a chimney be repaired in the rain?
Emergency measures like tarping or sealing an active leak can be done in wet weather. Permanent masonry work, crown rebuilds, and new flashing need dry conditions to cure and bond, so we schedule those on dry days and, ideally, in the summer window.
Why does my chimney only leak in winter?
Because that is when the water arrives. November, December, and January average about 17.8 inches of rain combined at Sea-Tac, and overnight temperatures near freezing open up cracks in saturated brick. The flaw is there all year; the wet season is what reveals it.
Does Seattle's mild winter mean freeze-thaw damage is not a concern?
No. Seattle has about 60 days a year where the temperature touches 32 F but only about 4 that stay frozen all day, so wet masonry freezes overnight and thaws by midday over and over. That repeated cycling on saturated brick is what causes spalling and cracking.
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