May is one of the warmer months of the year in Simi Valley, with average highs near 26.2°C and lows around 9.7°C (mean 18°C). It is one of the drier months, averaging 9 mm of rainfall and 52% relative humidity across the period.
May is one of the warmer months of the year in Simi Valley. Across 45 years of records, the warmest May in Simi Valley was 1997 — when the month averaged 22.4°C — while the coldest was 1998 at 13.2°C. Typical May days reach 26.2°C with nights near 9.7°C. The long-term May temperature trend is broadly flat.
May is one of the drier months in Simi Valley, averaging 9 mm of rainfall. The wettest May on record was 1998 with 84 mm, while the driest were 2004, 2007 and 2022, among others at 0 mm.
Relative humidity in Simi Valley during May averages 52%. The most humid May was 1998 at 72%, and the least humid was 1984 at 33%.
May receives about 7.4 kWh/m²/day of solar energy in Simi Valley. The sunniest Mays were 2012, 2020 and 2022, among others at 8 kWh/m²/day, and the cloudiest was 2019 at 6.5.
Average wind speed in Simi Valley during May is 2.3 m/s. The windiest May was 1984 at 3.4 m/s, while the calmest was 1992 at 1.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.1°C | 17.2°C | 18.9°C | 17.4°C | 18.3°C | +0.2°C |
| Avg High | 26.6°C | 25.2°C | 27.4°C | 25.4°C | 26.6°C | 0°C |
| Avg Low | 9.6°C | 9.2°C | 10.4°C | 9.4°C | 10.2°C | +0.6°C |
| Avg Rain | 3 mm | 15 mm | 10 mm | 11 mm | 4 mm | +2 mm |
May temperatures in Simi Valley have stayed relatively stable across the record.
May has ranged from a record low of 0.8°C (1991) to a record high of 37.3°C (2012).
Rainfall in May is one of the drier months, averaging 9 mm, with a wettest year of 84 mm.
Daytime highs and overnight lows have shifted differently — highs fell about 0.1°C per decade while lows rose 0.1°C per decade, narrowing the gap between day and night.
A good time to visit Simi Valley
May is a good time to visit Simi Valley, with days averaging 26.2°C and nights around 9.7°C (mean 18°C, warmer than Simi Valley's yearly average) and low rainfall. June and September are marginally more temperate, but May still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 27.6°C | 19.4°C | 11.2°C | 35.4°C | 6.0°C | 4 mm | 52% | 1.9 m/s | 7.2 |
| 2024 | 25.2°C | 17.1°C | 9.0°C | 30.2°C | 3.8°C | 2 mm | 63% | 1.9 m/s | 7.3 |
| 2023 | 23.0°C | 16.5°C | 10.0°C | 30.5°C | 4.9°C | 17 mm | 69% | 1.9 m/s | 6.7 |
| 2022 | 27.9°C | 18.8°C | 9.8°C | 33.8°C | 2.9°C | 0 mm | 43% | 2.4 m/s | 8 |
| 2021 | 28.5°C | 19.5°C | 10.5°C | 34.0°C | 4.3°C | 0 mm | 40% | 2.1 m/s | 7.9 |
| 2020 | 27.1°C | 18.8°C | 10.5°C | 34.9°C | 5.6°C | 3 mm | 53% | 2.3 m/s | 8 |
| 2019 | 21.5°C | 15.0°C | 8.5°C | 27.8°C | 4.7°C | 47 mm | 69% | 2.1 m/s | 6.5 |
| 2018 | 25.5°C | 17.9°C | 10.2°C | 32.5°C | 7.2°C | 6 mm | 58% | 1.9 m/s | 6.9 |
| 2017 | 25.9°C | 17.9°C | 9.9°C | 33.1°C | 4.0°C | 5 mm | 56% | 2.1 m/s | 7.3 |
| 2016 | 25.1°C | 17.3°C | 9.4°C | 34.6°C | 4.4°C | 7 mm | 58% | 1.9 m/s | 7 |
| 2015 | 24.4°C | 17.0°C | 9.7°C | 33.2°C | 5.6°C | 13 mm | 54% | 1.9 m/s | 6.8 |
| 2014 | 28.9°C | 19.9°C | 10.8°C | 35.7°C | 5.6°C | 2 mm | 36% | 2.3 m/s | 7.8 |
| 2013 | 27.8°C | 19.3°C | 10.8°C | 36.6°C | 5.9°C | 8 mm | 40% | 2.7 m/s | 7.7 |
| 2012 | 28.7°C | 19.2°C | 9.7°C | 37.3°C | 3.7°C | 0 mm | 42% | 2.4 m/s | 8 |
| 2011 | 23.0°C | 15.2°C | 7.3°C | 29.7°C | 2.4°C | 14 mm | 57% | 2.3 m/s | 7.7 |
| 2010 | 23.0°C | 15.1°C | 7.3°C | 30.5°C | 3.5°C | 4 mm | 56% | 2.7 m/s | 7.8 |
| 2009 | 29.5°C | 20.7°C | 12.0°C | 35.2°C | 9.1°C | 2 mm | 46% | 2.7 m/s | 7.7 |
| 2008 | 25.8°C | 17.6°C | 9.5°C | 37.1°C | 4.3°C | 6 mm | 49% | 2.2 m/s | 7.4 |
| 2007 | 27.9°C | 18.9°C | 9.9°C | 32.3°C | 5.3°C | 0 mm | 38% | 2.2 m/s | 7.9 |
| 2006 | 26.8°C | 18.8°C | 10.7°C | 33.4°C | 5.7°C | 20 mm | 60% | 2.1 m/s | 7.3 |
| 2005 | 25.6°C | 17.7°C | 9.9°C | 32.1°C | 5.1°C | 21 mm | 63% | 2.1 m/s | 7.5 |
| 2004 | 28.3°C | 19.4°C | 10.6°C | 36.0°C | 6.3°C | 0 mm | 40% | 2.3 m/s | 8 |
| 2003 | 25.1°C | 17.1°C | 9.2°C | 36.6°C | 2.5°C | 41 mm | 57% | 2.2 m/s | 7.2 |
| 2002 | 27.3°C | 18.1°C | 8.9°C | 35.5°C | 3.9°C | 4 mm | 43% | 2.1 m/s | 7.8 |
| 2001 | 29.6°C | 20.9°C | 12.1°C | 36.1°C | 6.7°C | 1 mm | 51% | 1.8 m/s | 7.7 |
| 2000 | 27.9°C | 19.3°C | 10.7°C | 36.2°C | 3.9°C | 2 mm | 50% | 2.6 m/s | 7.6 |
| 1999 | 25.8°C | 17.1°C | 8.4°C | 31.8°C | 3.7°C | 3 mm | 52% | 2.3 m/s | 7.4 |
| 1998 ❄️ 🌧️ | 19.4°C | 13.2°C | 6.9°C | 23.9°C | 3.8°C | 84 mm | 72% | 2.1 m/s | 6.6 |
| 1997 🔥 | 31.5°C | 22.4°C | 13.3°C | 36.9°C | 8.2°C | 1 mm | 40% | 2.5 m/s | 7.8 |
| 1996 | 27.3°C | 18.7°C | 10.1°C | 33.1°C | 6.0°C | 3 mm | 49% | 2.7 m/s | 7.8 |
| 1995 | 21.5°C | 14.8°C | 8.0°C | 29.1°C | 4.1°C | 18 mm | 69% | 2.2 m/s | 6.6 |
| 1994 | 24.9°C | 16.8°C | 8.6°C | 32.6°C | 4.1°C | 15 mm | 57% | 1.9 m/s | 6.8 |
| 1993 | 24.6°C | 17.0°C | 9.4°C | 29.0°C | 3.5°C | 1 mm | 60% | 2.5 m/s | 7.5 |
| 1992 | 27.1°C | 19.5°C | 11.8°C | 30.7°C | 8.1°C | 2 mm | 60% | 1.7 m/s | 7 |
| 1991 | 23.4°C | 15.1°C | 6.8°C | 30.7°C | 0.8°C | 1 mm | 55% | 2.5 m/s | 7.4 |
| 1990 | 26.5°C | 17.7°C | 8.9°C | 34.6°C | 5.9°C | 17 mm | 42% | 2.4 m/s | 7.3 |
| 1989 | 26.8°C | 18.0°C | 9.3°C | 32.9°C | 5.7°C | 5 mm | 44% | 2.5 m/s | 7.2 |
| 1988 | 25.8°C | 17.3°C | 8.7°C | 33.2°C | 2.0°C | 3 mm | 48% | 2.7 m/s | 7.2 |
| 1987 | 27.4°C | 19.4°C | 11.4°C | 34.1°C | 5.7°C | 6 mm | 44% | 2.2 m/s | 6.8 |
| 1986 | 26.5°C | 18.0°C | 9.4°C | 32.3°C | 4.2°C | 2 mm | 49% | 2.3 m/s | 7.6 |
| 1985 | 26.3°C | 17.5°C | 8.7°C | 32.4°C | 3.8°C | 2 mm | 43% | 2.2 m/s | 7.3 |
| 1984 | 30.7°C | 21.2°C | 11.7°C | 37.2°C | 4.9°C | 0 mm | 33% | 3.4 m/s | 7 |
| 1983 | 24.4°C | 16.6°C | 8.8°C | 32.2°C | 3.1°C | 2 mm | 61% | 2.8 m/s | — |
| 1982 | 25.7°C | 17.4°C | 9.1°C | 32.4°C | 2.9°C | 3 mm | 56% | 2.1 m/s | — |
| 1981 | 26.1°C | 17.6°C | 9.1°C | 32.3°C | 3.9°C | 3 mm | 48% | 2.5 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 26.2°C with lows near 9.7°C (mean 18°C), based on 45 years of NASA POWER data.
May averages 9 mm of rainfall in Simi Valley, one of the drier months. The wettest on record was 84 mm in 1998.
The hottest May reached 37.3°C in 2012. The coldest dipped to 0.8°C in 1991.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 0.2°C — but days and nights have moved in opposite directions. Overnight lows rose from 9.5°C to 10.1°C while daytime highs eased from 26.6°C to 26.4°C, narrowing the gap between day and night.
May is one of the warmer months of the year in Simi Valley and one of the drier months, so plan for around 26.2°C daytime highs and 9.7°C at night.
Not quite — May is the 7th coolest month in Simi Valley, averaging 18°C.
For May in Simi Valley, pack light layers you can adjust through the day, with typical highs of 26.2°C and lows of 9.7°C.
Relative humidity in May averages 52% — relatively dry.
Average wind speed in May is 2.3 m/s. The windiest May on record averaged 3.4 m/s (1984).
The wettest May on record was 1998 with 84 mm. On average, May sees 9 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 Simi Valley behaves each May, 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 May specifically, along with year-by-year records and how the month has changed over the decades.
