The year at a glance
The logic of the calendar is simple: Portland gets about two thirds of its 37 inches of rain between November and March, so the chimney is worked on when it is dry and burned when it is wet.
The national chimney standard calls for a yearly inspection with cleaning as needed, and the CDC gives the same advice on its carbon monoxide page; this calendar is about when to do that and what else falls due around it. Book the chimney sweep early in the year rather than in the fall rush.
| Month | Chimney and stove | Around the house |
|---|---|---|
| January | Burn season. After an ice storm or a tree strike, keep the fireplace cold until someone has looked at the stack; the January 2024 storm put trees onto roofs across the metro. | Check the county burn status before lighting on cold, still evenings; red days run noon to noon. |
| February | Book the sweep and Level 1 inspection for late winter or spring, while the flue is at its dirtiest and the schedule is open. | Test the carbon monoxide alarm and change its battery if that did not happen at the fall time change. |
| March | Sweep and inspect. Ask for the before and after flue photos and a note of anything the camera should look at more closely. | Washington County’s advisory season ends March 1; Multnomah County can call a red day in any month. |
| April | Read the inspection report and get bids for any repair it names; a crown or flashing job needs a dry spell, and an April bid is easier to schedule than a September one. | Walk the yard with binoculars: a missing cap, white staining, moss on the north face, flashing lifting at a corner. |
| May | Order and stack firewood if you burn. Split and stacked in May, covered on top with the sides open, it reaches the six months EPA Burn Wise calls the minimum before the heating season. | Check the dryer vent; long drying times or a stuck hood flap mean it needs cleaning. |
| June | Treat moss on the stack and the roof around it once the rain stops, so it is dead and dry before any water repellent goes on. | Clear the gutters; a gutter that overflows beside the chimney soaks the base flashing all winter. |
| July | The dry window opens: crown repair, tuckpointing, flashing, waterproofing, in that order. Mortar and sealers need dry masonry, and this is the month that gives it. | Portland Fire and Rescue’s seasonal ban on outdoor fires and fire pits has run from early summer into October in recent years; that covers outdoor burning, not the fireplace. |
| August | Cap and screen on by early August if the flue has none; Vaux’s swifts begin arriving in mid-August, and a flue they move into stays uncapped and unswept until they leave. | Wildfire smoke: on smoky days a closed damper, or a top-sealing damper, keeps the flue from pulling smoke into the house. |
| September | Swift month. If birds are using your chimney, the damper stays shut with no fire, sweep or cap until they have gone. Everyone else: the last dry-weather masonry work of the year. | Multnomah County wood burning exemptions expire September 30; renew before the first red day. |
| October | The heating season starts. Before the first fire: damper opens, cap in place, nothing on the smoke shelf, seasoned wood only. If the swifts have left, the cap goes on now. | If the furnace was replaced this year and the water heater still vents into the brick chimney, that flue needs a look; see the orphaned chimney guide below. |
| November | The wettest stretch of the year begins. Water in the firebox, a stain beside the chimney breast or a smell after rain is a leak; the fix waits for a dry day, but the diagnosis should not. | Washington County advisories begin November 1. Test the carbon monoxide alarm at the time change. |
| December | Burn clean and hot: small bright fires, air controls open, no overnight smolder. The wettest month and the coldest nights are when a flue runs coolest and creosote builds fastest. | Ice and east wind: after a storm, look for brick on the ground or a shifted cap before the next fire. |
Why the sweep belongs in spring rather than October
A flue is at its dirtiest in March, after a winter of fires, and a sweep then clears the creosote before it sits in the flue all summer giving off the smell that makes people call in July.
The CSIA procedure says to sweep any flue with an eighth of an inch or more of deposit, and that threshold is the same in March and October; what changes is the schedule. A spring sweep finds the cracked tile or open joint with five dry months ahead to fix it. The how often to sweep guide covers how burning habits move that number.
If a stove or insert heats the house all winter, add a midwinter check, because a flue in daily use builds deposits far faster than one serving a weekend fireplace. A chimney inspection without a sweep is the right booking when the question is only how much has built up.
The dry window for masonry, flashing and sealers
Mortar, crown coatings and water repellents need dry masonry and a dry forecast, and in Portland that means July and August, with June and September as the shoulders.
The airport normals show July and August each averaging about half an inch of rain and three or four rain days, against eighteen or nineteen in December and January. Tuckpointing in a wet month traps water behind fresh mortar, and a repellent on damp brick seals the damp in. A chimney waterproofing visit goes last, after the crown, joints and flashing are sound.
Freezing nights are the other reason. The airport records about 32 nights a year at or below freezing, nearly all in the wet months, and water sitting in a crack then spalls brick and splits crowns. Dry-season repair closes cracks before the first freeze, which is why a leak around the chimney noticed in November is diagnosed then and repaired the next summer unless water is reaching framing.
The swift window: cap by early August or wait until October
Vaux’s swifts roost in Portland chimneys from mid-August to mid-October on their way south, and a flue they are using is left alone, so an open chimney gets its cap before they arrive or after they leave.
The famous roost was the Chapman Elementary chimney in Northwest Portland for about forty years, until the birds moved to other chimneys after 2024; for a homeowner, any open flue is now a candidate. The birds are protected under federal law, and the rule is short: no fire, no sweep, no cap while they are in residence, damper closed. The swifts guide covers how to tell them from starlings.
A chimney cap installation booked for July settles it for good; a screened cap keeps swifts, starlings and raccoons out, and the flue stays yours in September.
Burn restrictions and smoke season
Red days are the days you do not light the fireplace, and in the metro they are called by the county rather than the state, so which rules apply depends on where you live.
Multnomah County can call a restriction in any month, with the heavy season running October through March: a red day means no wood burning without an exemption, a yellow day is the county asking households to consider limiting burning, and the call is posted by late morning and runs noon to noon. Exemptions, such as sole-source wood heat or income, expire September 30 and are renewed yearly.
Unincorporated Washington County, Hillsboro and Cornelius run an advisory season between November 1 and March 1 with the same colors and exemptions such as sole-source heat and low income. Our research found no ordinance for the other suburbs or for Clackamas County, where DEQ’s air quality advisories are the guide. The wood burning rules guide has the county-by-county detail and where to check the day’s status.
Wildfire smoke in August and September is a different problem: nothing to burn, but a flue to close. An open damper is a path for outside smoke into the house, one more argument for a damper that seals.
The checks that do not wait for a month
Some items on a chimney are not monthly; they are every time, and they override anything the table above says.
- Before the first fire of the season. Open the damper and look up with a flashlight for a nest or debris on the smoke shelf, and check the cap from the yard. A flue that smoked into the room last spring is not lit until it has been looked at.
- After any storm with Gorge wind or ice on the trees. Look for brick, mortar or cap parts on the ground, and keep the fireplace cold until the stack has been seen; a cracked liner or a shifted stack is a Level 2 question.
- When the fire will not draw, smoke rolls into the room, or the house smells of creosote on a warm wet day. Stop burning and call. Those are symptoms, not seasons.
- If there is a chimney fire. Get everyone out and call 911, in that order, before anything else. The flue stays cold afterward until a Level 2 inspection has looked at it.
- Carbon monoxide alarm. Test it regularly, change the battery on a fixed date, and keep one near every sleeping area, as the CDC advises, with another on the floor that has the fireplace, stove or furnace.
A new furnace that vents through the wall can leave the water heater alone in the old brick flue, and the orphaned chimney guide explains why that flue needs a look before winter.