When to change furnace filters
Furnace filters should be changed every 1 to 3 months during heating season; in most of the country 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 50F, 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 | |
|---|---|---|---|
| New York | NY | November to March | 4 |
| Los Angeles | CA | n/a | n/a |
| Chicago | IL | November to March | 4 |
| Houston | TX | n/a | n/a |
| Phoenix | AZ | n/a | n/a |
| Philadelphia | PA | November to March | 4 |
| San Antonio | TX | n/a | n/a |
| San Diego | CA | n/a | n/a |
| Dallas | TX | December to January | 2 |
| Austin | TX | n/a | n/a |
| Miami | FL | n/a | n/a |
| Tampa | FL | n/a | n/a |
| Atlanta | GA | December to February | 3 |
| Seattle | WA | November to March | 4 |
| Denver | CO | November to April | 4 |
| Boston | MA | November to April | 4 |
| Las Vegas | NV | December to January | 2 |
| Portland | OR | November to March | 4 |
| Minneapolis | MN | October to April | 5 |
| Detroit | MI | November to April | 4 |
| Nashville | TN | December to February | 3 |
| Charlotte | NC | December to February | 3 |
| Honolulu | HI | n/a | n/a |
| Anchorage | AK | September to May | 6 |
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Questions, answered plainly
How often should furnace filters be changed?
Every one to three months during heating season. For most 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 Minneapolis than in Atlanta. The schedule above counts the months your station's mean monthly temperature stays at or below 50F, then spaces filter changes about every two months through that period.
How this page was made
Data source: NOAA 30-year climate normals via the site dataset. Method: heating season is the contiguous run of months with mean temperature at or below 50F; 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.