When to change furnace filters
Furnace filters should be changed every 1 to 3 months during heating season; in most of Canada that means a fresh filter at first fire in fall, then every 2 months through spring. The exact months depend on your local heating season.
All change dates for the heating season.
Why a scheduled filter matters
A clogged filter makes the blower work harder, raises heating bills, and can shorten the heat exchanger's life. The cheap fix is changing the filter on a calendar, not waiting for airflow to drop.
The dates above use the 30-year mean monthly temperature at your nearest station. Heating season is the contiguous run of months with a mean temperature at or below 10 C, and the calendar adds a change every two months through that run.
Heating season and filter changes for major cities
| City | Heating season | Filter changes | |
|---|---|---|---|
| Victoria | BC | October to April | 5 |
| Vancouver | BC | November to April | 4 |
| Kelowna | BC | October to April | 5 |
| Calgary | AB | October to May | 5 |
| Edmonton | AB | October to April | 5 |
| Saskatoon Diefenbaker | SK | October to April | 5 |
| Regina | SK | October to April | 5 |
| Winnipeg Richardson | MB | October to April | 5 |
| Sudbury | ON | October to April | 5 |
| Ottawa Cda | ON | October to April | 5 |
| Toronto Lester B. Pearson | ON | October to April | 5 |
| Windsor | ON | November to April | 4 |
| Montreal/Pierre Elliott Trudeau | QC | October to April | 5 |
| Quebec/Jean Lesage | QC | October to April | 5 |
| Fredericton | NB | October to April | 5 |
| Halifax Stanfield | NS | October to May | 5 |
| Charlottetown | PE | October to May | 5 |
| Whitehorse | YT | September to May | 6 |
| Yellowknife | NT | September to May | 6 |
Related tools
Questions, answered plainly
How often should furnace filters be changed?
Every one to three months during heating season. For most Canadian homes, a fresh filter at first fire in fall and every two months through spring is a practical schedule. Pets, dust, and higher-MERV filters shorten the interval.
What MERV rating should I use?
MERV 8 to 11 suits most residential systems. Higher ratings trap more particles but can restrict airflow in older furnaces. Check the manufacturer label on the air handler or the existing filter frame.
Why does the schedule vary by place?
Heating season is longer in Winnipeg than in Vancouver. The schedule above counts the months your station's mean monthly temperature stays at or below 10 C, then spaces filter changes about every two months through that period.
How this page was made
Data source: Environment and Climate Change Canada 30-year climate normals via the site dataset. Method: heating season is the contiguous run of months with mean temperature at or below 10 C; filter changes are scheduled every two months from the season start, with count equal to ceil(heating months / 2) + 1. Verified 2026-06-12. Full notes on the methodology page.