September is one of the warmer months of the year in Oceanside, with average highs near 24.6°C and lows around 18.9°C (mean 21.8°C). It is one of the drier months, averaging 8 mm of rainfall and 72% relative humidity across the period.
September is one of the warmer months of the year in Oceanside. Across 45 years of records, the warmest September in Oceanside was 1984 — when the month averaged 24.9°C — while the coldest was 1986 at 19.2°C. Typical September days reach 24.6°C with nights near 18.9°C. The long-term September temperature trend is broadly flat.
September is one of the drier months in Oceanside, averaging 8 mm of rainfall. The wettest September on record was 2015 with 37 mm, while the driest was 2020 at 0 mm.
Relative humidity in Oceanside during September averages 72%. The most humid September was 2023 at 80%, and the least humid was 2012 at 67%.
September receives about 5.8 kWh/m²/day of solar energy in Oceanside. The sunniest September was 2014 at 6.3 kWh/m²/day, and the cloudiest was 2023 at 5.1.
Average wind speed in Oceanside during September is 2.3 m/s. The windiest September was 1986 at 2.8 m/s, while the calmest were 2009 and 2011 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 21.8°C | 21.6°C | 21.3°C | 22.0°C | 22.2°C | +0.4°C |
| Avg High | 24.8°C | 24.4°C | 24.2°C | 24.8°C | 24.9°C | +0.1°C |
| Avg Low | 18.8°C | 18.8°C | 18.4°C | 19.2°C | 19.6°C | +0.8°C |
| Avg Rain | 13 mm | 6 mm | 4 mm | 7 mm | 10 mm | -3 mm |
September temperatures in Oceanside have fallen by about 0.5°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 13.9°C (1999) to a record high of 35.8°C (1988).
Rainfall in September is one of the drier months, averaging 8 mm, with a wettest year of 37 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0°C per decade while lows rose 0.2°C per decade, narrowing the gap between day and night.
One of the best times to visit Oceanside
September is one of the best times to visit Oceanside. Expect days averaging 24.6°C and nights around 18.9°C (mean 21.8°C) — warmer than Oceanside's yearly average — with low rainfall (8 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 | 24.7°C | 22.2°C | 19.8°C | 28.5°C | 17.8°C | 26 mm | 77% | 2.5 m/s | 5.7 |
| 2024 | 24.3°C | 21.6°C | 18.8°C | 32.2°C | 15.8°C | 1 mm | 73% | 2.5 m/s | 5.8 |
| 2023 | 22.8°C | 20.8°C | 18.8°C | 28.0°C | 16.5°C | 3 mm | 80% | 2.6 m/s | 5.1 |
| 2022 | 26.3°C | 23.7°C | 21.2°C | 31.2°C | 17.3°C | 23 mm | 74% | 2.4 m/s | 5.7 |
| 2021 | 24.2°C | 21.3°C | 18.4°C | 29.3°C | 15.7°C | 7 mm | 73% | 2.3 m/s | 5.9 |
| 2020 | 27.0°C | 23.6°C | 20.3°C | 34.0°C | 16.9°C | 0 mm | 69% | 2.2 m/s | 5.9 |
| 2019 | 25.0°C | 22.3°C | 19.7°C | 28.6°C | 16.4°C | 3 mm | 73% | 2.4 m/s | 6 |
| 2018 | 23.9°C | 20.9°C | 17.9°C | 28.3°C | 16.0°C | 0 mm | 75% | 2.2 m/s | 6.1 |
| 2017 | 24.5°C | 22.0°C | 19.4°C | 32.2°C | 16.5°C | 4 mm | 74% | 2.6 m/s | 5.7 |
| 2016 | 24.1°C | 21.4°C | 18.6°C | 31.8°C | 15.2°C | 8 mm | 71% | 2.3 m/s | 5.9 |
| 2015 🌧️ | 26.4°C | 23.9°C | 21.5°C | 31.6°C | 17.9°C | 37 mm | 74% | 2.1 m/s | 6 |
| 2014 | 26.4°C | 23.7°C | 20.9°C | 31.4°C | 18.0°C | 2 mm | 72% | 2.4 m/s | 6.3 |
| 2013 | 24.5°C | 21.8°C | 19.1°C | 29.0°C | 16.0°C | 6 mm | 72% | 2.3 m/s | 6.1 |
| 2012 | 26.9°C | 23.6°C | 20.4°C | 34.6°C | 16.7°C | 2 mm | 67% | 2.2 m/s | 6.1 |
| 2011 | 23.0°C | 20.0°C | 17.0°C | 29.2°C | 15.2°C | 5 mm | 75% | 2 m/s | 5.5 |
| 2010 | 23.2°C | 20.2°C | 17.2°C | 32.4°C | 14.5°C | 4 mm | 72% | 2.3 m/s | 5.9 |
| 2009 | 25.5°C | 22.5°C | 19.4°C | 33.0°C | 16.9°C | 2 mm | 70% | 2 m/s | 6.2 |
| 2008 | 24.7°C | 21.8°C | 18.9°C | 29.0°C | 16.1°C | 2 mm | 73% | 2.3 m/s | 5.9 |
| 2007 | 23.2°C | 20.6°C | 18.0°C | 30.8°C | 15.7°C | 8 mm | 73% | 2.6 m/s | 6.1 |
| 2006 | 24.4°C | 21.3°C | 18.2°C | 29.0°C | 15.4°C | 2 mm | 71% | 2.3 m/s | 6.1 |
| 2005 | 23.0°C | 20.3°C | 17.5°C | 29.5°C | 14.6°C | 5 mm | 71% | 2.1 m/s | 6.1 |
| 2004 | 25.2°C | 22.2°C | 19.3°C | 30.8°C | 16.2°C | 2 mm | 69% | 2.1 m/s | 6.2 |
| 2003 | 24.5°C | 21.5°C | 18.5°C | 28.9°C | 16.7°C | 2 mm | 76% | 2.1 m/s | 5.8 |
| 2002 | 24.5°C | 21.5°C | 18.6°C | 30.0°C | 16.4°C | 8 mm | 70% | 2.2 m/s | 5.6 |
| 2001 | 23.2°C | 20.3°C | 17.5°C | 28.2°C | 15.5°C | 2 mm | 75% | 2.2 m/s | 5.9 |
| 2000 | 24.3°C | 21.4°C | 18.5°C | 29.8°C | 16.6°C | 7 mm | 72% | 2.3 m/s | 5.7 |
| 1999 | 22.3°C | 19.5°C | 16.7°C | 31.0°C | 13.9°C | 5 mm | 75% | 2.4 m/s | 5.7 |
| 1998 | 23.2°C | 21.0°C | 18.8°C | 31.1°C | 16.5°C | 6 mm | 76% | 2.5 m/s | 5.4 |
| 1997 | 26.4°C | 23.7°C | 21.0°C | 29.5°C | 18.1°C | 32 mm | 74% | 2.2 m/s | 5.8 |
| 1996 | 23.7°C | 21.1°C | 18.5°C | 27.3°C | 16.8°C | 1 mm | 76% | 2.5 m/s | 5.8 |
| 1995 | 25.0°C | 22.1°C | 19.2°C | 28.6°C | 17.1°C | 2 mm | 71% | 2.3 m/s | 6 |
| 1994 | 24.2°C | 21.5°C | 18.7°C | 27.9°C | 16.3°C | 0 mm | 72% | 2.4 m/s | 5.7 |
| 1993 | 24.3°C | 21.1°C | 18.0°C | 29.1°C | 14.9°C | 1 mm | 69% | 2.5 m/s | 5.6 |
| 1992 | 25.3°C | 22.3°C | 19.3°C | 29.0°C | 17.1°C | 0 mm | 70% | 2.2 m/s | 6 |
| 1991 | 24.1°C | 21.1°C | 18.1°C | 28.1°C | 15.1°C | 7 mm | 75% | 2.2 m/s | 5.5 |
| 1990 | 25.1°C | 22.2°C | 19.3°C | 29.4°C | 17.1°C | 3 mm | 71% | 2.3 m/s | 6 |
| 1989 | 24.7°C | 21.6°C | 18.4°C | 28.3°C | 15.5°C | 9 mm | 67% | 2.3 m/s | 5.9 |
| 1988 | 24.8°C | 21.5°C | 18.2°C | 35.8°C | 15.6°C | 1 mm | 69% | 2.3 m/s | 5.3 |
| 1987 | 24.5°C | 21.4°C | 18.3°C | 30.7°C | 15.9°C | 8 mm | 73% | 2.1 m/s | 5.5 |
| 1986 ❄️ | 21.9°C | 19.2°C | 16.6°C | 27.5°C | 14.8°C | 33 mm | 73% | 2.8 m/s | 5.6 |
| 1985 | 23.3°C | 20.7°C | 18.1°C | 26.6°C | 16.0°C | 9 mm | 70% | 2.5 m/s | 5.5 |
| 1984 🔥 | 28.1°C | 24.9°C | 21.7°C | 34.0°C | 19.2°C | 6 mm | 69% | 2.4 m/s | 5.3 |
| 1983 | 26.2°C | 23.4°C | 20.5°C | 30.8°C | 17.7°C | 28 mm | 71% | 2.4 m/s | — |
| 1982 | 24.2°C | 21.5°C | 18.9°C | 30.5°C | 15.8°C | 23 mm | 71% | 2.5 m/s | — |
| 1981 | 25.1°C | 21.7°C | 18.4°C | 28.9°C | 16.3°C | 5 mm | 67% | 2.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 24.6°C with lows near 18.9°C (mean 21.8°C), based on 45 years of NASA POWER data.
September averages 8 mm of rainfall in Oceanside, one of the drier months. The wettest on record was 37 mm in 2015.
The hottest September reached 35.8°C in 1988. The coldest dipped to 13.9°C in 1999.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have fallen by about 0.5°C. Daytime highs moved from 25.4°C to 24.5°C and overnight lows from 19.5°C to 19.4°C over the same span.
September is one of the warmer months of the year in Oceanside and one of the drier months, so plan for around 24.6°C daytime highs and 18.9°C at night.
Not quite — September is the 11th coolest month in Oceanside, averaging 21.8°C.
For September in Oceanside, pack light layers you can adjust through the day, with typical highs of 24.6°C and lows of 18.9°C.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 2.3 m/s. The windiest September on record averaged 2.8 m/s (1986).
The wettest September on record was 2015 with 37 mm. On average, September sees 8 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 Oceanside 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.
