May is one of the warmer months of the year in Richland, with average highs near 23.1°C and lows around 8.9°C (mean 16°C). It is about average for rainfall, averaging 21 mm of rainfall and 51% relative humidity across the period.
May is one of the warmer months of the year in Richland. Across 45 years of records, the warmest May in Richland was 2023 — when the month averaged 19.8°C — while the coldest was 1984 at 12.8°C. Typical May days reach 23.1°C with nights near 8.9°C. The long-term trend is warming, about 0.3°C per decade.
May is about average for rainfall in Richland, averaging 21 mm of rainfall. The wettest May on record was 2010 with 41 mm, while the driest was 1992 at 2 mm.
Relative humidity in Richland during May averages 51%. The most humid May was 1998 at 58%, and the least humid was 1992 at 41%.
May receives about 6.4 kWh/m²/day of solar energy in Richland. The sunniest May was 2009 at 7.2 kWh/m²/day, and the cloudiest was 1998 at 5.6.
Average wind speed in Richland during May is 2.4 m/s. The windiest May was 1984 at 2.8 m/s, while the calmest was 2018 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.4°C | 15.8°C | 16.2°C | 16.5°C | 16.1°C | +0.7°C |
| Avg High | 22.5°C | 22.8°C | 23.4°C | 23.5°C | 23.3°C | +0.8°C |
| Avg Low | 8.2°C | 8.9°C | 9.0°C | 9.4°C | 8.8°C | +0.6°C |
| Avg Rain | 19 mm | 24 mm | 18 mm | 24 mm | 22 mm | +2 mm |
May temperatures in Richland have risen by about 1°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -0.7°C (1999) to a record high of 39.1°C (1986).
Rainfall in May is about average for rainfall, averaging 21 mm, with a wettest year of 41 mm.
A good time to visit Richland
May is a good time to visit Richland, with days averaging 23.1°C and nights around 8.9°C (mean 16°C, warmer than Richland's yearly average) and low rainfall. August and June 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 | 22.7°C | 15.0°C | 7.3°C | 31.1°C | 1.0°C | 25 mm | 55% | 2.2 m/s | 6.8 |
| 2024 | 22.8°C | 15.1°C | 7.5°C | 32.2°C | 0.8°C | 19 mm | 51% | 2.4 m/s | 6.8 |
| 2023 🔥 | 27.0°C | 19.8°C | 12.7°C | 35.0°C | 7.2°C | 12 mm | 49% | 2 m/s | 6.8 |
| 2022 | 19.7°C | 13.3°C | 6.9°C | 25.9°C | 1.3°C | 30 mm | 57% | 2.4 m/s | 5.9 |
| 2021 | 24.4°C | 16.9°C | 9.4°C | 33.2°C | 3.9°C | 4 mm | 43% | 2.6 m/s | 7.1 |
| 2020 | 23.5°C | 16.4°C | 9.2°C | 35.0°C | 3.0°C | 39 mm | 51% | 2.6 m/s | 6.4 |
| 2019 | 25.1°C | 17.9°C | 10.7°C | 32.1°C | 4.1°C | 19 mm | 49% | 2.3 m/s | 6.4 |
| 2018 | 26.5°C | 19.4°C | 12.3°C | 32.8°C | 5.5°C | 16 mm | 51% | 1.9 m/s | 6.6 |
| 2017 | 23.6°C | 16.4°C | 9.2°C | 33.4°C | 2.7°C | 18 mm | 53% | 2.1 m/s | 6.6 |
| 2016 | 24.6°C | 17.5°C | 10.4°C | 30.7°C | 7.2°C | 25 mm | 49% | 2.4 m/s | 6.7 |
| 2015 | 25.5°C | 18.3°C | 11.1°C | 33.2°C | 5.0°C | 30 mm | 48% | 2.1 m/s | 6.8 |
| 2014 | 24.5°C | 17.2°C | 9.8°C | 31.6°C | 5.2°C | 9 mm | 48% | 2.4 m/s | 6.8 |
| 2013 | 23.6°C | 16.4°C | 9.3°C | 34.6°C | 0.6°C | 29 mm | 51% | 2.2 m/s | 6.5 |
| 2012 | 22.1°C | 15.0°C | 8.0°C | 33.4°C | 1.6°C | 12 mm | 47% | 2.5 m/s | 6.5 |
| 2011 | 19.9°C | 13.2°C | 6.5°C | 26.7°C | 1.6°C | 38 mm | 56% | 2.4 m/s | 6 |
| 2010 🌧️ | 19.9°C | 13.5°C | 7.0°C | 29.5°C | 1.3°C | 41 mm | 53% | 2.3 m/s | 5.9 |
| 2009 | 24.1°C | 16.2°C | 8.2°C | 36.2°C | 2.4°C | 17 mm | 48% | 2.5 m/s | 7.2 |
| 2008 | 23.9°C | 16.5°C | 9.2°C | 36.5°C | 1.1°C | 16 mm | 50% | 2.3 m/s | 6.1 |
| 2007 | 24.4°C | 16.5°C | 8.7°C | 33.4°C | 1.7°C | 11 mm | 47% | 2.3 m/s | 7 |
| 2006 | 24.0°C | 16.8°C | 9.5°C | 37.1°C | 0.6°C | 26 mm | 49% | 2.3 m/s | 6.6 |
| 2005 | 24.0°C | 17.1°C | 10.3°C | 34.6°C | 5.4°C | 31 mm | 52% | 2.2 m/s | 6.1 |
| 2004 | 22.4°C | 16.1°C | 9.7°C | 29.5°C | 6.7°C | 21 mm | 51% | 2.4 m/s | 5.9 |
| 2003 | 21.9°C | 15.3°C | 8.8°C | 33.4°C | 1.9°C | 9 mm | 51% | 2.2 m/s | 6.1 |
| 2002 | 21.9°C | 15.0°C | 8.1°C | 27.7°C | 1.4°C | 16 mm | 49% | 2.5 m/s | 6.2 |
| 2001 | 25.2°C | 16.8°C | 8.5°C | 37.4°C | 1.7°C | 8 mm | 44% | 2.3 m/s | 7.1 |
| 2000 | 22.0°C | 15.4°C | 8.9°C | 30.8°C | 2.2°C | 24 mm | 50% | 2.7 m/s | 6.4 |
| 1999 | 20.7°C | 13.5°C | 6.3°C | 34.0°C | -0.7°C | 16 mm | 50% | 2.6 m/s | 6.6 |
| 1998 | 21.9°C | 15.6°C | 9.2°C | 31.9°C | 5.3°C | 29 mm | 58% | 2.5 m/s | 5.6 |
| 1997 | 24.1°C | 17.2°C | 10.3°C | 32.6°C | 1.7°C | 21 mm | 56% | 2.1 m/s | 6.5 |
| 1996 | 19.5°C | 13.1°C | 6.6°C | 27.3°C | 0.7°C | 28 mm | 57% | 2.5 m/s | 6.3 |
| 1995 | 23.8°C | 16.6°C | 9.4°C | 33.0°C | 4.1°C | 16 mm | 51% | 2.3 m/s | 6.6 |
| 1994 | 23.9°C | 16.9°C | 9.9°C | 33.0°C | 4.0°C | 30 mm | 50% | 2.2 m/s | 5.9 |
| 1993 | 25.4°C | 18.2°C | 11.0°C | 34.4°C | 4.3°C | 30 mm | 54% | 2.6 m/s | 6.2 |
| 1992 | 26.8°C | 18.6°C | 10.4°C | 35.2°C | 3.0°C | 2 mm | 41% | 2.3 m/s | 7 |
| 1991 | 20.8°C | 14.1°C | 7.3°C | 25.5°C | 2.4°C | 38 mm | 55% | 2.6 m/s | 5.7 |
| 1990 | 21.2°C | 14.6°C | 8.1°C | 32.6°C | 2.4°C | 32 mm | 53% | 2.4 m/s | 5.9 |
| 1989 | 22.0°C | 15.1°C | 8.2°C | 29.4°C | 4.3°C | 29 mm | 53% | 2.3 m/s | 6.2 |
| 1988 | 22.4°C | 15.2°C | 7.9°C | 33.6°C | 1.0°C | 21 mm | 49% | 2.6 m/s | 5.8 |
| 1987 | 24.9°C | 17.5°C | 10.2°C | 35.7°C | 4.7°C | 17 mm | 48% | 2.5 m/s | 6.4 |
| 1986 | 22.8°C | 15.6°C | 8.5°C | 39.1°C | 1.9°C | 20 mm | 53% | 2.3 m/s | 6.2 |
| 1985 | 23.5°C | 16.1°C | 8.7°C | 33.4°C | 1.5°C | 9 mm | 50% | 2.5 m/s | 6.8 |
| 1984 ❄️ | 19.2°C | 12.8°C | 6.5°C | 32.1°C | 2.5°C | 22 mm | 57% | 2.8 m/s | 5.9 |
| 1983 | 24.2°C | 16.6°C | 9.0°C | 37.6°C | 4.0°C | 16 mm | 53% | 2.4 m/s | — |
| 1982 | 21.7°C | 14.5°C | 7.2°C | 30.2°C | 0.9°C | 10 mm | 50% | 2.3 m/s | — |
| 1981 | 21.6°C | 14.8°C | 8.0°C | 29.2°C | 2.7°C | 29 mm | 52% | 2.1 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 23.1°C with lows near 8.9°C (mean 16°C), based on 45 years of NASA POWER data.
May averages 21 mm of rainfall in Richland, about average for rainfall. The wettest on record was 41 mm in 2010.
The hottest May reached 39.1°C in 1986. The coldest dipped to -0.7°C in 1999.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1°C. Daytime highs moved from 22°C to 23.3°C and overnight lows from 7.9°C to 8.8°C over the same span.
May is one of the warmer months of the year in Richland and about average for rainfall, so plan for around 23.1°C daytime highs and 8.9°C at night.
Not quite — May is the 8th coolest month in Richland, averaging 16°C.
For May in Richland, pack light layers you can adjust through the day, with typical highs of 23.1°C and lows of 8.9°C.
Relative humidity in May averages 51% — relatively dry.
Average wind speed in May is 2.4 m/s. The windiest May on record averaged 2.8 m/s (1984).
The wettest May on record was 2010 with 41 mm. On average, May sees 21 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 Richland 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.
