September is one of the warmer months of the year in Saint-Lazare, with average highs near 21.2°C and lows around 9.9°C (mean 15.6°C). It is about average for rainfall, averaging 86 mm of rainfall and 76% relative humidity across the period.
September is one of the warmer months of the year in Saint-Lazare. Across 45 years of records, the warmest September in Saint-Lazare was 2015 — when the month averaged 18.8°C — while the coldest was 1986 at 12.6°C. Typical September days reach 21.2°C with nights near 9.9°C. The long-term trend is warming, about 0.8°C per decade.
September is about average for rainfall in Saint-Lazare, averaging 86 mm of rainfall. The wettest September on record was 2010 with 169 mm, while the driest was 2023 at 25 mm.
Relative humidity in Saint-Lazare during September averages 76%. The most humid September was 1982 at 82%, and the least humid was 2025 at 66%.
September receives about 3.9 kWh/m²/day of solar energy in Saint-Lazare. The sunniest September was 2016 at 4.5 kWh/m²/day, and the cloudiest was 1990 at 3.1.
Average wind speed in Saint-Lazare during September is 0.9 m/s. The windiest Septembers were 1992, 1997 and 2010, among others at 1 m/s, while the calmest was 2023 at 0.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.3°C | 14.7°C | 15.9°C | 16.5°C | 16.9°C | +2.6°C |
| Avg High | 19.8°C | 20.2°C | 21.7°C | 22.1°C | 22.8°C | +3°C |
| Avg Low | 8.8°C | 9.1°C | 10.1°C | 10.8°C | 11.0°C | +2.2°C |
| Avg Rain | 93 mm | 87 mm | 92 mm | 93 mm | 53 mm | -40 mm |
September temperatures in Saint-Lazare have risen by about 2.6°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -2.3°C (1991) to a record high of 34°C (2023).
Rainfall in September is about average for rainfall, averaging 86 mm, with a wettest year of 169 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.9°C per decade while lows rose 0.7°C per decade, widening the gap between day and night.
One of the best times to visit Saint-Lazare
September is one of the best times to visit Saint-Lazare. Expect days averaging 21.2°C and nights around 9.9°C (mean 15.6°C) — warmer than Saint-Lazare's yearly average — with higher rainfall (86 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 | 23.9°C | 17.4°C | 10.9°C | 29.1°C | 3.3°C | 41 mm | 66% | 0.8 m/s | 4.4 |
| 2024 | 23.6°C | 17.8°C | 12.0°C | 28.8°C | 5.8°C | 45 mm | 75% | 0.9 m/s | 4.3 |
| 2023 | 24.6°C | 18.2°C | 11.9°C | 34.0°C | 6.9°C | 25 mm | 71% | 0.7 m/s | 4.3 |
| 2022 | 21.4°C | 15.6°C | 9.8°C | 30.0°C | 3.6°C | 75 mm | 74% | 0.8 m/s | 3.8 |
| 2021 | 22.6°C | 17.2°C | 11.7°C | 28.2°C | 6.3°C | 77 mm | 71% | 0.9 m/s | 3.8 |
| 2020 | 20.7°C | 15.0°C | 9.4°C | 27.7°C | 1.7°C | 53 mm | 72% | 0.9 m/s | 3.6 |
| 2019 | 21.5°C | 15.5°C | 9.5°C | 27.4°C | 3.9°C | 103 mm | 77% | 0.8 m/s | 3.9 |
| 2018 | 23.1°C | 17.5°C | 11.9°C | 32.1°C | 3.2°C | 88 mm | 74% | 0.9 m/s | 3.8 |
| 2017 | 22.9°C | 17.4°C | 11.9°C | 30.6°C | 5.0°C | 46 mm | 80% | 0.8 m/s | 4.3 |
| 2016 | 23.6°C | 17.5°C | 11.4°C | 31.8°C | 3.9°C | 43 mm | 70% | 0.9 m/s | 4.5 |
| 2015 🔥 | 24.8°C | 18.8°C | 12.8°C | 32.2°C | 5.2°C | 95 mm | 73% | 0.8 m/s | 4.2 |
| 2014 | 21.0°C | 15.2°C | 9.3°C | 28.2°C | -0.5°C | 66 mm | 78% | 0.9 m/s | 3.8 |
| 2013 | 19.8°C | 14.4°C | 8.9°C | 28.8°C | 3.0°C | 110 mm | 78% | 0.9 m/s | 3.9 |
| 2012 | 21.1°C | 15.5°C | 9.8°C | 28.8°C | 3.5°C | 122 mm | 73% | 0.9 m/s | 3.8 |
| 2011 | 22.1°C | 16.9°C | 11.7°C | 27.3°C | 3.6°C | 93 mm | 81% | 0.8 m/s | 4 |
| 2010 🌧️ | 20.8°C | 15.8°C | 10.9°C | 32.3°C | 5.4°C | 169 mm | 80% | 1 m/s | 3.3 |
| 2009 | 20.7°C | 14.8°C | 8.8°C | 25.7°C | 3.2°C | 61 mm | 76% | 0.9 m/s | 4.4 |
| 2008 | 21.9°C | 16.0°C | 10.0°C | 31.1°C | 2.6°C | 65 mm | 78% | 0.8 m/s | 3.8 |
| 2007 | 22.6°C | 16.4°C | 10.2°C | 31.7°C | 3.4°C | 65 mm | 73% | 0.9 m/s | 4.4 |
| 2006 | 19.4°C | 14.3°C | 9.1°C | 24.6°C | 3.1°C | 106 mm | 82% | 0.9 m/s | 3.3 |
| 2005 | 22.2°C | 16.6°C | 11.1°C | 28.7°C | 3.8°C | 142 mm | 79% | 0.9 m/s | 4.1 |
| 2004 | 21.7°C | 16.1°C | 10.4°C | 26.4°C | 4.5°C | 104 mm | 80% | 0.8 m/s | 4.2 |
| 2003 | 22.8°C | 17.1°C | 11.4°C | 29.2°C | 6.0°C | 110 mm | 75% | 0.9 m/s | 4 |
| 2002 | 24.2°C | 17.9°C | 11.7°C | 33.5°C | 4.4°C | 83 mm | 69% | 0.9 m/s | 4.3 |
| 2001 | 22.0°C | 16.2°C | 10.5°C | 31.9°C | 4.0°C | 87 mm | 72% | 0.9 m/s | 4.1 |
| 2000 | 19.2°C | 13.7°C | 8.2°C | 28.3°C | -1.7°C | 98 mm | 79% | 0.9 m/s | 3.6 |
| 1999 | 23.0°C | 17.4°C | 11.9°C | 33.6°C | 4.0°C | 142 mm | 76% | 0.9 m/s | 3.5 |
| 1998 | 21.4°C | 15.7°C | 10.1°C | 27.1°C | 2.7°C | 68 mm | 76% | 0.9 m/s | 3.9 |
| 1997 | 20.0°C | 14.5°C | 9.0°C | 26.1°C | 1.0°C | 82 mm | 76% | 1 m/s | 3.4 |
| 1996 | 21.5°C | 16.4°C | 11.3°C | 29.8°C | 4.4°C | 102 mm | 77% | 0.9 m/s | 3.7 |
| 1995 | 19.5°C | 13.3°C | 7.0°C | 26.9°C | 1.8°C | 59 mm | 67% | 0.9 m/s | 4 |
| 1994 | 20.4°C | 14.8°C | 9.1°C | 25.6°C | 4.8°C | 63 mm | 77% | 0.9 m/s | 3.8 |
| 1993 | 18.8°C | 13.4°C | 8.1°C | 27.9°C | 0.0°C | 110 mm | 75% | 0.9 m/s | 3.4 |
| 1992 | 19.4°C | 14.1°C | 8.9°C | 27.3°C | 0.1°C | 94 mm | 79% | 1 m/s | 3.4 |
| 1991 | 18.8°C | 13.2°C | 7.7°C | 27.2°C | -2.3°C | 69 mm | 72% | 0.9 m/s | 3.8 |
| 1990 | 19.4°C | 13.8°C | 8.1°C | 26.5°C | 1.9°C | 82 mm | 77% | 0.9 m/s | 3.1 |
| 1989 | 20.8°C | 15.0°C | 9.3°C | 28.1°C | -0.3°C | 88 mm | 76% | 0.9 m/s | 3.7 |
| 1988 | 19.6°C | 13.8°C | 8.0°C | 27.2°C | 0.7°C | 69 mm | 75% | 0.9 m/s | 3.9 |
| 1987 | 19.5°C | 14.4°C | 9.4°C | 26.4°C | 0.1°C | 111 mm | 79% | 0.9 m/s | 3.8 |
| 1986 ❄️ | 17.9°C | 12.6°C | 7.4°C | 23.3°C | 1.4°C | 138 mm | 81% | 0.9 m/s | 3.3 |
| 1985 | 21.5°C | 15.5°C | 9.6°C | 28.0°C | 4.1°C | 80 mm | 74% | 0.9 m/s | 4.1 |
| 1984 | 19.1°C | 13.4°C | 7.6°C | 25.8°C | 1.2°C | 31 mm | 74% | 0.9 m/s | 4.4 |
| 1983 | 22.5°C | 16.5°C | 10.6°C | 31.0°C | 4.6°C | 71 mm | 71% | 0.9 m/s | — |
| 1982 | 19.4°C | 14.1°C | 8.8°C | 27.0°C | 3.7°C | 110 mm | 82% | 0.9 m/s | — |
| 1981 | 18.3°C | 13.6°C | 8.9°C | 25.0°C | -0.3°C | 138 mm | 81% | 1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 21.2°C with lows near 9.9°C (mean 15.6°C), based on 45 years of NASA POWER data.
September averages 86 mm of rainfall in Saint-Lazare, about average for rainfall. The wettest on record was 169 mm in 2010.
The hottest September reached 34°C in 2023. The coldest dipped to -2.3°C in 1991.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.6°C. Daytime highs moved from 20.2°C to 23.2°C and overnight lows from 9.1°C to 11.3°C over the same span.
September is one of the warmer months of the year in Saint-Lazare and about average for rainfall, so plan for around 21.2°C daytime highs and 9.9°C at night.
Not quite — September is the 9th coolest month in Saint-Lazare, averaging 15.6°C.
For September in Saint-Lazare, pack light layers you can adjust through the day, with typical highs of 21.2°C and lows of 9.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 76% — quite humid.
Average wind speed in September is 0.9 m/s. The windiest September on record averaged 1 m/s (1981).
The wettest September on record was 2010 with 169 mm. On average, September sees 86 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 Saint-Lazare 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.
