September is one of the warmer months of the year in Yellowknife, with average highs near 10.4°C and lows around 4°C (mean 7.2°C). It is about average for rainfall, averaging 43 mm of rainfall and 78% relative humidity across the period.
September is one of the warmer months of the year in Yellowknife. Across 45 years of records, the warmest September in Yellowknife was 2025 — when the month averaged 11.1°C — while the coldest was 2018 at 1.5°C. Typical September days reach 10.4°C with nights near 4°C. The long-term trend is warming, about 0.5°C per decade.
September is about average for rainfall in Yellowknife, averaging 43 mm of rainfall. The wettest September on record was 2008 with 124 mm, while the driest was 2022 at 8 mm.
Relative humidity in Yellowknife during September averages 78%. The most humid September was 2005 at 84%, and the least humid was 1993 at 72%.
September receives about 2.5 kWh/m²/day of solar energy in Yellowknife. The sunniest Septembers were 1986, 2012 and 2022 at 2.8 kWh/m²/day, and the cloudiest were 2005 and 2008 at 2.1.
Average wind speed in Yellowknife during September is 4.1 m/s. The windiest Septembers were 1985 and 2016 at 4.8 m/s, while the calmest was 1984 at 3.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 6.5°C | 7.1°C | 6.6°C | 7.4°C | 9.1°C | +2.6°C |
| Avg High | 9.8°C | 10.4°C | 9.7°C | 10.6°C | 12.3°C | +2.5°C |
| Avg Low | 3.2°C | 3.8°C | 3.6°C | 4.1°C | 5.9°C | +2.7°C |
| Avg Rain | 37 mm | 43 mm | 58 mm | 38 mm | 35 mm | -3 mm |
September temperatures in Yellowknife have risen by about 4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -13.2°C (1983) to a record high of 23.4°C (2013).
Rainfall in September is about average for rainfall, averaging 43 mm, with a wettest year of 124 mm.
One of the best times to visit Yellowknife
September is one of the best times to visit Yellowknife. Expect days averaging 10.4°C and nights around 4°C (mean 7.2°C) — warmer than Yellowknife's yearly average — with moderate rainfall (43 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 🔥 | 14.5°C | 11.1°C | 7.8°C | 21.9°C | 3.2°C | 41 mm | 78% | 4 m/s | 2.4 |
| 2024 | 12.4°C | 9.3°C | 6.2°C | 21.7°C | 0.0°C | 41 mm | 81% | 3.9 m/s | 2.5 |
| 2023 | 13.6°C | 10.5°C | 7.5°C | 20.8°C | -0.9°C | 29 mm | 77% | 3.7 m/s | 2.3 |
| 2022 | 13.0°C | 9.3°C | 5.5°C | 21.0°C | -1.5°C | 8 mm | 77% | 4.2 m/s | 2.8 |
| 2021 | 11.3°C | 8.5°C | 5.6°C | 19.3°C | -0.2°C | 46 mm | 82% | 4 m/s | 2.2 |
| 2020 | 9.2°C | 6.1°C | 2.9°C | 15.4°C | -2.5°C | 42 mm | 80% | 3.7 m/s | 2.7 |
| 2019 | 9.6°C | 6.8°C | 4.0°C | 14.7°C | -1.3°C | 54 mm | 84% | 3.9 m/s | 2.4 |
| 2018 ❄️ | 4.1°C | 1.5°C | -1.2°C | 13.6°C | -6.5°C | 37 mm | 80% | 4.3 m/s | 2.6 |
| 2017 | 13.0°C | 9.7°C | 6.3°C | 20.7°C | 2.3°C | 21 mm | 76% | 4 m/s | 2.6 |
| 2016 | 10.7°C | 7.3°C | 3.9°C | 17.6°C | -2.3°C | 61 mm | 78% | 4.8 m/s | 2.5 |
| 2015 | 10.4°C | 7.2°C | 4.1°C | 19.4°C | -4.4°C | 38 mm | 77% | 4.2 m/s | 2.6 |
| 2014 | 9.1°C | 5.9°C | 2.8°C | 16.8°C | -1.5°C | 29 mm | 76% | 3.9 m/s | 2.5 |
| 2013 | 12.9°C | 9.4°C | 5.8°C | 23.4°C | 0.4°C | 26 mm | 78% | 4.3 m/s | 2.4 |
| 2012 | 13.8°C | 10.2°C | 6.5°C | 20.8°C | 0.1°C | 36 mm | 76% | 3.9 m/s | 2.8 |
| 2011 | 13.0°C | 9.4°C | 5.8°C | 20.3°C | -1.4°C | 31 mm | 78% | 4.1 m/s | 2.7 |
| 2010 | 9.1°C | 6.3°C | 3.5°C | 19.3°C | -2.8°C | 43 mm | 80% | 3.4 m/s | 2.4 |
| 2009 | 13.0°C | 9.9°C | 6.9°C | 21.5°C | 0.7°C | 54 mm | 82% | 4 m/s | 2.2 |
| 2008 🌧️ | 7.2°C | 4.2°C | 1.3°C | 14.0°C | -3.7°C | 124 mm | 82% | 3.9 m/s | 2.1 |
| 2007 | 6.3°C | 3.5°C | 0.7°C | 14.7°C | -7.1°C | 69 mm | 81% | 3.9 m/s | 2.2 |
| 2006 | 12.4°C | 9.3°C | 6.2°C | 19.7°C | -0.7°C | 27 mm | 81% | 3.5 m/s | 2.4 |
| 2005 | 7.6°C | 5.0°C | 2.5°C | 16.5°C | -8.4°C | 109 mm | 84% | 3.7 m/s | 2.1 |
| 2004 | 8.2°C | 5.0°C | 1.8°C | 16.6°C | -2.8°C | 44 mm | 79% | 4.7 m/s | 2.3 |
| 2003 | 11.3°C | 8.0°C | 4.7°C | 20.8°C | -2.0°C | 27 mm | 76% | 4.2 m/s | 2.6 |
| 2002 | 10.0°C | 6.9°C | 3.9°C | 18.0°C | -3.6°C | 26 mm | 79% | 4.4 m/s | 2.5 |
| 2001 | 12.8°C | 9.5°C | 6.2°C | 19.6°C | -0.6°C | 44 mm | 80% | 4.2 m/s | 2.7 |
| 2000 | 8.1°C | 5.0°C | 1.9°C | 14.4°C | -4.7°C | 57 mm | 79% | 4.7 m/s | 2.6 |
| 1999 | 10.6°C | 7.2°C | 3.9°C | 17.0°C | -3.6°C | 48 mm | 76% | 4.6 m/s | 2.6 |
| 1998 | 11.6°C | 8.5°C | 5.4°C | 17.8°C | -0.3°C | 52 mm | 79% | 3.8 m/s | 2.5 |
| 1997 | 13.0°C | 9.5°C | 5.9°C | 20.8°C | 0.0°C | 41 mm | 78% | 4 m/s | 2.5 |
| 1996 | 12.0°C | 8.9°C | 5.8°C | 20.0°C | -5.8°C | 72 mm | 77% | 4.6 m/s | 2.4 |
| 1995 | 10.6°C | 7.1°C | 3.6°C | 20.2°C | -2.4°C | 52 mm | 79% | 4.2 m/s | 2.6 |
| 1994 | 12.0°C | 8.3°C | 4.6°C | 20.7°C | -3.0°C | 26 mm | 72% | 3.9 m/s | 2.3 |
| 1993 | 9.5°C | 5.8°C | 2.2°C | 19.7°C | -5.7°C | 26 mm | 72% | 4.1 m/s | 2.7 |
| 1992 | 6.0°C | 3.0°C | 0.1°C | 14.2°C | -5.7°C | 35 mm | 72% | 3.5 m/s | 2.4 |
| 1991 | 9.2°C | 6.2°C | 3.3°C | 14.3°C | -2.9°C | 43 mm | 81% | 4.1 m/s | 2.6 |
| 1990 | 9.3°C | 6.1°C | 3.0°C | 17.6°C | -2.6°C | 30 mm | 78% | 4.2 m/s | 2.5 |
| 1989 | 10.3°C | 7.1°C | 3.8°C | 21.7°C | -3.3°C | 37 mm | 73% | 4 m/s | 2.7 |
| 1988 | 9.9°C | 6.7°C | 3.5°C | 20.4°C | -2.9°C | 32 mm | 80% | 4.4 m/s | 2.5 |
| 1987 | 12.2°C | 8.9°C | 5.6°C | 19.7°C | -2.2°C | 44 mm | 80% | 4.1 m/s | 2.4 |
| 1986 | 10.8°C | 7.2°C | 3.7°C | 18.1°C | -4.7°C | 9 mm | 77% | 3.6 m/s | 2.8 |
| 1985 | 8.0°C | 4.8°C | 1.6°C | 17.7°C | -2.9°C | 17 mm | 78% | 4.8 m/s | 2.7 |
| 1984 | 8.4°C | 5.3°C | 2.2°C | 15.7°C | -2.5°C | 22 mm | 74% | 3.2 m/s | 2.7 |
| 1983 | 8.3°C | 5.1°C | 1.9°C | 19.1°C | -13.2°C | 56 mm | 78% | 4.2 m/s | — |
| 1982 | 10.4°C | 7.1°C | 3.8°C | 17.7°C | -2.2°C | 50 mm | 80% | 4.1 m/s | — |
| 1981 | 9.5°C | 6.2°C | 2.9°C | 18.7°C | -2.1°C | 69 mm | 78% | 4.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 10.4°C with lows near 4°C (mean 7.2°C), based on 45 years of NASA POWER data.
September averages 43 mm of rainfall in Yellowknife, about average for rainfall. The wettest on record was 124 mm in 2008.
The hottest September reached 23.4°C in 2013. The coldest dipped to -13.2°C in 1983.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 4°C. Daytime highs moved from 8.9°C to 13°C and overnight lows from 2.5°C to 6.5°C over the same span.
September is one of the warmer months of the year in Yellowknife and about average for rainfall, so plan for around 10.4°C daytime highs and 4°C at night.
Not quite — September is the 9th coolest month in Yellowknife, averaging 7.2°C.
For September in Yellowknife, pack warm layers and a jacket for chilly mornings, with typical highs of 10.4°C and lows of 4°C.
Relative humidity in September averages 78% — quite humid.
Average wind speed in September is 4.1 m/s. The windiest September on record averaged 4.8 m/s (1985).
The wettest September on record was 2008 with 124 mm. On average, September sees 43 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Yellowknife behaves each September, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for September specifically, along with year-by-year records and how the month has changed over the decades.
