May is close to El Cajon's year-round average, with average highs near 24.7°C and lows around 10.8°C (mean 17.8°C). It is one of the drier months, averaging 8 mm of rainfall and 62% relative humidity across the period.
May is close to El Cajon's year-round average. Across 45 years of records, the warmest May in El Cajon was 1997 — when the month averaged 22°C — while the coldest was 1998 at 14.2°C. Typical May days reach 24.7°C with nights near 10.8°C. The long-term May temperature trend is broadly flat.
May is one of the drier months in El Cajon, averaging 8 mm of rainfall. The wettest May on record was 1998 with 46 mm, while the driest was 2009 at 0 mm.
Relative humidity in El Cajon during May averages 62%. The most humid May was 1998 at 77%, and the least humid was 1984 at 42%.
May receives about 7.6 kWh/m²/day of solar energy in El Cajon. The sunniest May was 2020 at 8.3 kWh/m²/day, and the cloudiest was 2019 at 6.5.
Average wind speed in El Cajon during May is 2.7 m/s. The windiest Mays were 1990 and 1998 at 3.2 m/s, while the calmest were 1997 and 2001 at 2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 18.2°C | 17.1°C | 18.6°C | 17.2°C | 17.7°C | -0.5°C |
| Avg High | 25.6°C | 23.7°C | 25.9°C | 23.8°C | 24.6°C | -1°C |
| Avg Low | 10.8°C | 10.4°C | 11.3°C | 10.6°C | 10.8°C | 0°C |
| Avg Rain | 4 mm | 11 mm | 4 mm | 14 mm | 4 mm | 0 mm |
May temperatures in El Cajon have fallen by about 0.6°C between 1981–1985 and 2021–2025.
May has ranged from a record low of 4.3°C (1999) to a record high of 39.5°C (1984).
Rainfall in May is one of the drier months, averaging 8 mm, with a wettest year of 46 mm.
Daytime highs and overnight lows have shifted differently — highs fell about 0.2°C per decade while lows rose 0°C per decade, narrowing the gap between day and night.
A good time to visit El Cajon
May is a good time to visit El Cajon, with days averaging 24.7°C and nights around 10.8°C (mean 17.8°C, close to El Cajon'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 | 25.4°C | 18.6°C | 11.8°C | 35.7°C | 9.0°C | 7 mm | 64% | 2.6 m/s | 7.3 |
| 2024 | 23.0°C | 16.3°C | 9.6°C | 28.5°C | 7.7°C | 3 mm | 71% | 2.7 m/s | 8 |
| 2023 | 21.8°C | 16.1°C | 10.5°C | 29.1°C | 7.7°C | 8 mm | 73% | 2.9 m/s | 7.2 |
| 2022 | 25.9°C | 18.3°C | 10.6°C | 34.3°C | 5.9°C | 0 mm | 59% | 2.6 m/s | 8.1 |
| 2021 | 25.6°C | 18.0°C | 10.5°C | 32.1°C | 6.6°C | 1 mm | 60% | 2.7 m/s | 8.1 |
| 2020 | 26.2°C | 19.1°C | 12.0°C | 33.2°C | 9.0°C | 2 mm | 65% | 2.4 m/s | 8.3 |
| 2019 | 20.4°C | 15.3°C | 10.2°C | 26.4°C | 7.6°C | 38 mm | 76% | 3.1 m/s | 6.5 |
| 2018 | 24.0°C | 17.5°C | 11.0°C | 33.2°C | 7.7°C | 3 mm | 64% | 3 m/s | 7.7 |
| 2017 | 24.1°C | 17.5°C | 10.9°C | 33.4°C | 6.9°C | 21 mm | 65% | 2.6 m/s | 7.4 |
| 2016 | 23.5°C | 17.2°C | 10.9°C | 31.0°C | 9.0°C | 12 mm | 69% | 2.9 m/s | 7.2 |
| 2015 | 22.6°C | 16.7°C | 10.7°C | 32.0°C | 8.2°C | 40 mm | 68% | 2.9 m/s | 6.8 |
| 2014 | 26.9°C | 19.7°C | 12.5°C | 35.9°C | 7.9°C | 1 mm | 50% | 2.8 m/s | 8 |
| 2013 | 26.1°C | 18.9°C | 11.7°C | 36.1°C | 8.7°C | 11 mm | 58% | 2.8 m/s | 7.8 |
| 2012 | 26.1°C | 18.3°C | 10.5°C | 35.1°C | 7.8°C | 0 mm | 58% | 2.4 m/s | 8.2 |
| 2011 | 21.8°C | 15.4°C | 9.1°C | 31.4°C | 6.5°C | 15 mm | 65% | 3.1 m/s | 7.7 |
| 2010 | 22.6°C | 15.7°C | 8.9°C | 30.5°C | 5.5°C | 0 mm | 65% | 2.7 m/s | 8.2 |
| 2009 | 27.8°C | 20.0°C | 12.1°C | 33.6°C | 9.3°C | 0 mm | 58% | 2.3 m/s | 7.9 |
| 2008 | 23.6°C | 17.0°C | 10.4°C | 35.9°C | 5.9°C | 6 mm | 61% | 2.7 m/s | 7.5 |
| 2007 | 26.3°C | 18.6°C | 10.8°C | 32.3°C | 8.1°C | 0 mm | 53% | 2.5 m/s | 7.9 |
| 2006 | 26.6°C | 19.0°C | 11.5°C | 33.6°C | 7.6°C | 8 mm | 62% | 2.2 m/s | 7.8 |
| 2005 | 24.9°C | 18.2°C | 11.5°C | 33.2°C | 8.0°C | 4 mm | 67% | 2.5 m/s | 8 |
| 2004 | 26.3°C | 19.2°C | 12.1°C | 35.6°C | 8.6°C | 0 mm | 56% | 2.7 m/s | 8.2 |
| 2003 | 24.3°C | 17.5°C | 10.6°C | 38.3°C | 4.8°C | 20 mm | 65% | 2.4 m/s | 7.3 |
| 2002 | 25.1°C | 17.3°C | 9.6°C | 35.3°C | 6.7°C | 0 mm | 58% | 2.7 m/s | 8.1 |
| 2001 | 28.3°C | 20.4°C | 12.4°C | 35.9°C | 8.6°C | 1 mm | 58% | 2 m/s | 7.7 |
| 2000 | 26.1°C | 19.1°C | 12.1°C | 35.8°C | 9.3°C | 4 mm | 61% | 2.5 m/s | 7.8 |
| 1999 | 23.4°C | 16.2°C | 9.0°C | 29.7°C | 4.3°C | 1 mm | 65% | 2.8 m/s | 7.8 |
| 1998 ❄️ 🌧️ | 19.0°C | 14.2°C | 9.3°C | 24.0°C | 7.0°C | 46 mm | 77% | 3.2 m/s | 7.1 |
| 1997 🔥 | 30.0°C | 22.0°C | 14.0°C | 35.1°C | 10.2°C | 1 mm | 53% | 2 m/s | 7.9 |
| 1996 | 24.9°C | 18.0°C | 11.0°C | 34.7°C | 8.2°C | 2 mm | 63% | 2.8 m/s | 8.2 |
| 1995 | 19.7°C | 14.6°C | 9.4°C | 30.7°C | 7.3°C | 23 mm | 76% | 3.1 m/s | 6.6 |
| 1994 | 23.6°C | 16.7°C | 9.7°C | 29.4°C | 7.6°C | 4 mm | 68% | 2.6 m/s | 7 |
| 1993 | 24.6°C | 18.0°C | 11.3°C | 29.7°C | 8.4°C | 7 mm | 68% | 2.8 m/s | 7.9 |
| 1992 | 26.6°C | 19.4°C | 12.1°C | 31.6°C | 9.5°C | 9 mm | 67% | 2.3 m/s | 7.3 |
| 1991 | 22.0°C | 15.3°C | 8.6°C | 30.3°C | 6.2°C | 1 mm | 66% | 3.1 m/s | 7.9 |
| 1990 | 23.3°C | 16.6°C | 9.9°C | 33.1°C | 7.5°C | 12 mm | 64% | 3.2 m/s | 7.6 |
| 1989 | 25.3°C | 18.1°C | 11.0°C | 33.3°C | 8.6°C | 5 mm | 56% | 2.9 m/s | 7.5 |
| 1988 | 25.3°C | 18.0°C | 10.7°C | 33.6°C | 5.0°C | 6 mm | 56% | 2.5 m/s | 7.3 |
| 1987 | 26.3°C | 19.4°C | 12.4°C | 33.9°C | 8.1°C | 4 mm | 55% | 2.5 m/s | 7 |
| 1986 | 25.6°C | 18.1°C | 10.5°C | 33.3°C | 6.4°C | 1 mm | 56% | 2.6 m/s | 7.9 |
| 1985 | 24.4°C | 17.1°C | 9.9°C | 32.6°C | 6.8°C | 1 mm | 59% | 2.6 m/s | 7.7 |
| 1984 | 30.4°C | 21.8°C | 13.1°C | 39.5°C | 7.4°C | 0 mm | 42% | 2.2 m/s | 7.7 |
| 1983 | 24.3°C | 17.3°C | 10.2°C | 32.5°C | 6.3°C | 2 mm | 64% | 2.5 m/s | — |
| 1982 | 23.7°C | 16.7°C | 9.7°C | 31.0°C | 7.2°C | 6 mm | 66% | 2.7 m/s | — |
| 1981 | 25.0°C | 17.6°C | 10.1°C | 31.9°C | 6.9°C | 9 mm | 58% | 2.6 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 24.7°C with lows near 10.8°C (mean 17.8°C), based on 45 years of NASA POWER data.
May averages 8 mm of rainfall in El Cajon, one of the drier months. The wettest on record was 46 mm in 1998.
The hottest May reached 39.5°C in 1984. The coldest dipped to 4.3°C in 1999.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have fallen by about 0.6°C. Daytime highs moved from 25.6°C to 24.3°C and overnight lows from 10.6°C to 10.6°C over the same span.
May is close to El Cajon's year-round average and one of the drier months, so plan for around 24.7°C daytime highs and 10.8°C at night.
Not quite — May is the 7th coolest month in El Cajon, averaging 17.8°C.
For May in El Cajon, pack light layers you can adjust through the day, with typical highs of 24.7°C and lows of 10.8°C.
Relative humidity in May averages 62% — moderately humid.
Average wind speed in May is 2.7 m/s. The windiest May on record averaged 3.2 m/s (1990).
The wettest May on record was 1998 with 46 mm. On average, May 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 El Cajon 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.
