September is one of the warmer months of the year in Williams Lake, with average highs near 18°C and lows around 4.4°C (mean 11.2°C). It is about average for rainfall, averaging 49 mm of rainfall and 68% relative humidity across the period.
September is one of the warmer months of the year in Williams Lake. Across 45 years of records, the warmest September in Williams Lake was 2025 — when the month averaged 15.2°C — while the coldest was 2018 at 8.1°C. Typical September days reach 18°C with nights near 4.4°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Williams Lake, averaging 49 mm of rainfall. The wettest September on record was 2004 with 114 mm, while the driest was 1993 at 6 mm.
Relative humidity in Williams Lake during September averages 68%. The most humid September was 2004 at 83%, and the least humid was 1987 at 58%.
September receives about 3.6 kWh/m²/day of solar energy in Williams Lake. The sunniest Septembers were 1990 and 1995 at 4.4 kWh/m²/day, and the cloudiest were 1992, 2004 and 2018 at 3.
Average wind speed in Williams Lake during September is 0.2 m/s. The windiest Septembers were 2022, 2023 and 2025, among others at 0.2 m/s, while the calmest were 2020, 2021 and 2024, among others at 0.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 10.3°C | 11.5°C | 10.7°C | 11.0°C | 13.1°C | +2.8°C |
| Avg High | 17.1°C | 18.8°C | 17.4°C | 17.5°C | 19.8°C | +2.7°C |
| Avg Low | 3.5°C | 4.3°C | 4.0°C | 4.6°C | 6.4°C | +2.9°C |
| Avg Rain | 50 mm | 38 mm | 54 mm | 57 mm | 48 mm | -1 mm |
September temperatures in Williams Lake have risen by about 3.6°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -5.9°C (2019) to a record high of 34.9°C (1988).
Rainfall in September is about average for rainfall, averaging 49 mm, with a wettest year of 114 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.3°C per decade while lows rose 0.5°C per decade, narrowing the gap between day and night.
One of the best times to visit Williams Lake
September is one of the best times to visit Williams Lake. Expect days averaging 18°C and nights around 4.4°C (mean 11.2°C) — warmer than Williams Lake's yearly average — with moderate rainfall (49 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 🔥 | 22.0°C | 15.2°C | 8.5°C | 33.1°C | 1.0°C | 53 mm | 71% | 0.2 m/s | 3.3 |
| 2024 | 20.0°C | 13.1°C | 6.2°C | 32.3°C | -3.8°C | 70 mm | 68% | 0.1 m/s | 3.7 |
| 2023 | 18.7°C | 11.9°C | 5.2°C | 27.1°C | 1.2°C | 29 mm | 67% | 0.2 m/s | 3.7 |
| 2022 | 21.6°C | 13.9°C | 6.2°C | 32.0°C | 0.9°C | 32 mm | 64% | 0.2 m/s | 4.2 |
| 2021 | 17.5°C | 11.3°C | 5.1°C | 27.3°C | 0.2°C | 51 mm | 69% | 0.1 m/s | 3.4 |
| 2020 | 19.3°C | 13.2°C | 7.0°C | 27.9°C | 0.9°C | 56 mm | 75% | 0.1 m/s | 3.5 |
| 2019 | 16.0°C | 10.4°C | 4.8°C | 27.9°C | -5.9°C | 86 mm | 78% | 0.1 m/s | 3.1 |
| 2018 ❄️ | 13.5°C | 8.1°C | 2.7°C | 23.1°C | -2.3°C | 93 mm | 78% | 0.1 m/s | 3 |
| 2017 | 18.5°C | 12.1°C | 5.6°C | 28.8°C | -3.2°C | 49 mm | 69% | 0.2 m/s | 3.1 |
| 2016 | 15.3°C | 9.3°C | 3.4°C | 24.1°C | -1.8°C | 74 mm | 76% | 0.2 m/s | 3.4 |
| 2015 | 15.9°C | 9.4°C | 2.9°C | 27.8°C | -1.9°C | 68 mm | 72% | 0.1 m/s | 3.4 |
| 2014 | 19.1°C | 11.9°C | 4.8°C | 26.8°C | -4.3°C | 32 mm | 68% | 0.2 m/s | 4 |
| 2013 | 19.8°C | 13.1°C | 6.5°C | 31.7°C | -2.6°C | 54 mm | 68% | 0.1 m/s | 3.9 |
| 2012 | 21.0°C | 13.2°C | 5.4°C | 27.7°C | 0.2°C | 16 mm | 62% | 0.2 m/s | 4.1 |
| 2011 | 20.1°C | 13.1°C | 6.2°C | 29.1°C | 1.4°C | 35 mm | 64% | 0.1 m/s | 3.7 |
| 2010 | 15.5°C | 9.3°C | 3.2°C | 25.7°C | -3.1°C | 63 mm | 75% | 0.1 m/s | 3.2 |
| 2009 | 20.3°C | 13.0°C | 5.7°C | 29.7°C | -2.9°C | 58 mm | 64% | 0.1 m/s | 3.7 |
| 2008 | 18.2°C | 11.1°C | 3.9°C | 26.2°C | -3.0°C | 25 mm | 66% | 0.2 m/s | 3.9 |
| 2007 | 15.8°C | 9.4°C | 3.0°C | 25.8°C | -2.8°C | 69 mm | 71% | 0.2 m/s | 3.5 |
| 2006 | 19.4°C | 12.2°C | 5.1°C | 31.8°C | -3.0°C | 56 mm | 68% | 0.2 m/s | 3.7 |
| 2005 | 15.7°C | 9.1°C | 2.5°C | 21.0°C | -2.7°C | 59 mm | 72% | 0.2 m/s | 3.5 |
| 2004 🌧️ | 13.5°C | 8.4°C | 3.3°C | 18.0°C | -2.3°C | 114 mm | 83% | 0.1 m/s | 3 |
| 2003 | 19.1°C | 11.7°C | 4.4°C | 31.2°C | -1.3°C | 37 mm | 64% | 0.2 m/s | 3.5 |
| 2002 | 16.4°C | 10.1°C | 3.8°C | 24.1°C | -0.4°C | 45 mm | 69% | 0.2 m/s | 3.2 |
| 2001 | 19.0°C | 11.9°C | 4.8°C | 26.4°C | -0.7°C | 38 mm | 65% | 0.1 m/s | 3.9 |
| 2000 | 16.7°C | 10.0°C | 3.3°C | 23.6°C | -4.6°C | 38 mm | 72% | 0.2 m/s | 3.5 |
| 1999 | 17.0°C | 10.2°C | 3.4°C | 25.3°C | -2.6°C | 53 mm | 69% | 0.2 m/s | 3.8 |
| 1998 | 19.4°C | 12.1°C | 4.9°C | 25.7°C | 0.3°C | 44 mm | 69% | 0.2 m/s | 3.7 |
| 1997 | 19.4°C | 12.2°C | 5.1°C | 27.4°C | -0.1°C | 59 mm | 69% | 0.1 m/s | 3.8 |
| 1996 | 15.0°C | 9.0°C | 3.1°C | 24.7°C | -3.1°C | 83 mm | 74% | 0.2 m/s | 3.3 |
| 1995 | 20.4°C | 12.6°C | 4.8°C | 26.0°C | -1.6°C | 19 mm | 64% | 0.2 m/s | 4.4 |
| 1994 | 20.0°C | 13.0°C | 5.9°C | 24.8°C | 1.8°C | 25 mm | 64% | 0.2 m/s | 3.2 |
| 1993 | 20.0°C | 11.9°C | 3.8°C | 27.8°C | -3.6°C | 6 mm | 58% | 0.2 m/s | 4.3 |
| 1992 | 15.2°C | 8.8°C | 2.3°C | 23.1°C | -5.4°C | 52 mm | 66% | 0.1 m/s | 3 |
| 1991 | 19.8°C | 12.1°C | 4.3°C | 27.2°C | 0.0°C | 16 mm | 64% | 0.2 m/s | 4 |
| 1990 | 21.6°C | 13.3°C | 5.0°C | 26.7°C | 0.8°C | 20 mm | 59% | 0.2 m/s | 4.4 |
| 1989 | 19.2°C | 11.8°C | 4.3°C | 25.6°C | -1.0°C | 18 mm | 66% | 0.2 m/s | 4.2 |
| 1988 | 17.7°C | 10.5°C | 3.2°C | 34.9°C | -2.4°C | 42 mm | 65% | 0.2 m/s | 3.4 |
| 1987 | 21.7°C | 13.6°C | 5.4°C | 28.9°C | 0.4°C | 13 mm | 58% | 0.2 m/s | 3.6 |
| 1986 | 15.7°C | 9.0°C | 2.4°C | 22.3°C | -2.4°C | 55 mm | 69% | 0.1 m/s | 3.5 |
| 1985 | 14.9°C | 8.4°C | 2.0°C | 22.3°C | -3.8°C | 72 mm | 66% | 0.2 m/s | 3.6 |
| 1984 | 14.8°C | 8.3°C | 1.8°C | 23.3°C | -3.6°C | 67 mm | 67% | 0.2 m/s | 3.4 |
| 1983 | 14.8°C | 8.4°C | 2.1°C | 22.1°C | -5.6°C | 55 mm | 67% | 0.2 m/s | — |
| 1982 | 17.1°C | 11.2°C | 5.2°C | 26.1°C | -1.6°C | 74 mm | 76% | 0.2 m/s | — |
| 1981 | 18.1°C | 11.4°C | 4.7°C | 31.1°C | -4.3°C | 50 mm | 66% | 0.1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 18°C with lows near 4.4°C (mean 11.2°C), based on 45 years of NASA POWER data.
September averages 49 mm of rainfall in Williams Lake, about average for rainfall. The wettest on record was 114 mm in 2004.
The hottest September reached 34.9°C in 1988. The coldest dipped to -5.9°C in 2019.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 3.6°C. Daytime highs moved from 15.9°C to 20°C and overnight lows from 3.2°C to 6.2°C over the same span.
September is one of the warmer months of the year in Williams Lake and about average for rainfall, so plan for around 18°C daytime highs and 4.4°C at night.
Not quite — September is the 9th coolest month in Williams Lake, averaging 11.2°C.
For September in Williams Lake, pack warm layers and a jacket for chilly mornings, with typical highs of 18°C and lows of 4.4°C.
Relative humidity in September averages 68% — moderately humid.
Average wind speed in September is 0.2 m/s. The windiest September on record averaged 0.2 m/s (1982).
The wettest September on record was 2004 with 114 mm. On average, September sees 49 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 Williams Lake 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.
