May is one of the warmer months of the year in Harrisburg, with average highs near 21.2°C and lows around 9.4°C (mean 15.3°C). It is a relatively wet time of year, averaging 106 mm of rainfall and 78% relative humidity across the period.
May is one of the warmer months of the year in Harrisburg. Across 45 years of records, the warmest May in Harrisburg was 2015 — when the month averaged 18.7°C — while the coldest was 1997 at 12.5°C. Typical May days reach 21.2°C with nights near 9.4°C. The long-term trend is warming, about 0.5°C per decade.
May is a relatively wet time of year in Harrisburg, averaging 106 mm of rainfall. The wettest May on record was 1989 with 221 mm, while the driest was 2023 at 13 mm.
Relative humidity in Harrisburg during May averages 78%. The most humid May was 2011 at 84%, and the least humid was 2023 at 68%.
May receives about 5.4 kWh/m²/day of solar energy in Harrisburg. The sunniest May was 2007 at 6.8 kWh/m²/day, and the cloudiest was 2003 at 3.8.
Average wind speed in Harrisburg during May is 0.5 m/s. The windiest May was 1997 at 0.6 m/s, while the calmest were 2018, 2023 and 2024, among others at 0.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.7°C | 14.7°C | 15.1°C | 16.7°C | 15.6°C | +0.9°C |
| Avg High | 20.7°C | 20.7°C | 21.1°C | 22.4°C | 21.4°C | +0.7°C |
| Avg Low | 8.7°C | 8.6°C | 9.2°C | 11.0°C | 9.7°C | +1°C |
| Avg Rain | 122 mm | 90 mm | 96 mm | 119 mm | 109 mm | -13 mm |
May temperatures in Harrisburg have risen by about 1.5°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -2.4°C (2020) to a record high of 33.5°C (2006).
Rainfall in May is a relatively wet time of year, averaging 106 mm, with a wettest year of 221 mm.
A good time to visit Harrisburg
May is a good time to visit Harrisburg, with days averaging 21.2°C and nights around 9.4°C (mean 15.3°C, warmer than Harrisburg's yearly average) and higher 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 | 21.4°C | 16.0°C | 10.6°C | 28.0°C | 4.8°C | 218 mm | 79% | 0.5 m/s | 4.7 |
| 2024 | 22.8°C | 17.6°C | 12.5°C | 29.2°C | 6.6°C | 117 mm | 82% | 0.4 m/s | 5.1 |
| 2023 | 21.8°C | 14.9°C | 7.9°C | 29.0°C | 0.5°C | 13 mm | 68% | 0.4 m/s | 6.5 |
| 2022 | 22.5°C | 16.4°C | 10.4°C | 31.0°C | 2.2°C | 143 mm | 80% | 0.5 m/s | 5.3 |
| 2021 | 21.1°C | 15.0°C | 9.0°C | 30.1°C | 1.9°C | 101 mm | 74% | 0.5 m/s | 5.5 |
| 2020 | 18.9°C | 13.4°C | 7.9°C | 27.6°C | -2.4°C | 60 mm | 78% | 0.5 m/s | 5.5 |
| 2019 | 22.1°C | 16.9°C | 11.7°C | 27.6°C | 4.7°C | 171 mm | 82% | 0.5 m/s | 5 |
| 2018 | 24.4°C | 18.6°C | 12.9°C | 30.5°C | 2.3°C | 144 mm | 83% | 0.4 m/s | 4.9 |
| 2017 | 20.2°C | 14.6°C | 9.0°C | 30.2°C | 0.3°C | 134 mm | 78% | 0.5 m/s | 4.6 |
| 2016 | 20.2°C | 14.9°C | 9.6°C | 30.6°C | 0.4°C | 98 mm | 80% | 0.4 m/s | 4.9 |
| 2015 🔥 | 25.2°C | 18.7°C | 12.2°C | 31.0°C | 2.9°C | 65 mm | 72% | 0.4 m/s | 6 |
| 2014 | 21.4°C | 15.6°C | 9.8°C | 28.5°C | 3.3°C | 112 mm | 79% | 0.5 m/s | 5.2 |
| 2013 | 21.4°C | 15.4°C | 9.5°C | 30.6°C | -0.8°C | 82 mm | 78% | 0.5 m/s | 5.9 |
| 2012 | 23.9°C | 18.5°C | 13.1°C | 30.0°C | 4.1°C | 157 mm | 80% | 0.4 m/s | 5.3 |
| 2011 | 22.0°C | 16.9°C | 11.8°C | 31.5°C | 3.4°C | 147 mm | 84% | 0.5 m/s | 5 |
| 2010 | 22.8°C | 16.8°C | 10.7°C | 30.7°C | -0.2°C | 86 mm | 77% | 0.5 m/s | 5.4 |
| 2009 | 20.9°C | 15.4°C | 10.0°C | 27.7°C | 4.4°C | 147 mm | 79% | 0.5 m/s | 5 |
| 2008 | 19.2°C | 13.3°C | 7.3°C | 27.1°C | 1.8°C | 115 mm | 79% | 0.5 m/s | 5.1 |
| 2007 | 23.2°C | 16.3°C | 9.3°C | 32.0°C | 2.6°C | 45 mm | 73% | 0.4 m/s | 6.8 |
| 2006 | 21.0°C | 15.1°C | 9.1°C | 33.5°C | 2.3°C | 74 mm | 74% | 0.5 m/s | 5.7 |
| 2005 | 18.9°C | 12.8°C | 6.6°C | 27.1°C | -0.1°C | 37 mm | 75% | 0.5 m/s | 5.9 |
| 2004 | 23.9°C | 18.4°C | 12.9°C | 28.4°C | 2.4°C | 131 mm | 81% | 0.5 m/s | 5.4 |
| 2003 | 18.7°C | 13.9°C | 9.2°C | 24.8°C | 4.2°C | 130 mm | 84% | 0.5 m/s | 3.8 |
| 2002 | 20.8°C | 14.3°C | 7.7°C | 29.0°C | -0.2°C | 118 mm | 74% | 0.5 m/s | 5.7 |
| 2001 | 22.4°C | 15.9°C | 9.5°C | 30.7°C | 3.0°C | 64 mm | 70% | 0.5 m/s | 5.8 |
| 2000 | 22.1°C | 16.0°C | 10.0°C | 29.3°C | 1.6°C | 95 mm | 79% | 0.5 m/s | 5.2 |
| 1999 | 22.9°C | 16.2°C | 9.4°C | 31.7°C | 5.0°C | 51 mm | 70% | 0.5 m/s | 5.9 |
| 1998 | 22.4°C | 17.1°C | 11.7°C | 30.3°C | 6.4°C | 136 mm | 82% | 0.4 m/s | 5.5 |
| 1997 ❄️ | 18.8°C | 12.5°C | 6.1°C | 27.5°C | -0.7°C | 81 mm | 72% | 0.6 m/s | 5.8 |
| 1996 | 19.0°C | 13.2°C | 7.5°C | 29.1°C | -1.2°C | 87 mm | 81% | 0.5 m/s | 5 |
| 1995 | 20.3°C | 14.3°C | 8.3°C | 28.4°C | 0.9°C | 80 mm | 77% | 0.5 m/s | 5 |
| 1994 | 19.2°C | 12.9°C | 6.5°C | 28.1°C | 0.9°C | 76 mm | 76% | 0.5 m/s | 5.8 |
| 1993 | 21.3°C | 15.3°C | 9.2°C | 27.6°C | 4.2°C | 56 mm | 78% | 0.4 m/s | 5.6 |
| 1992 | 19.6°C | 13.5°C | 7.5°C | 28.7°C | 1.7°C | 100 mm | 77% | 0.5 m/s | 5.2 |
| 1991 | 24.2°C | 18.1°C | 11.9°C | 30.8°C | 3.1°C | 61 mm | 78% | 0.5 m/s | 6.3 |
| 1990 | 19.2°C | 13.6°C | 8.0°C | 24.2°C | 3.3°C | 168 mm | 78% | 0.5 m/s | 4.7 |
| 1989 🌧️ | 19.1°C | 13.9°C | 8.7°C | 27.4°C | 2.8°C | 221 mm | 82% | 0.5 m/s | 4.3 |
| 1988 | 21.0°C | 15.2°C | 9.4°C | 28.2°C | 2.2°C | 146 mm | 80% | 0.5 m/s | 5.3 |
| 1987 | 21.4°C | 15.1°C | 8.9°C | 29.6°C | 0.7°C | 83 mm | 81% | 0.4 m/s | 5.3 |
| 1986 | 21.9°C | 15.8°C | 9.6°C | 28.6°C | -1.4°C | 62 mm | 78% | 0.5 m/s | 6.3 |
| 1985 | 21.6°C | 15.5°C | 9.3°C | 27.2°C | 0.1°C | 144 mm | 78% | 0.5 m/s | 5.6 |
| 1984 | 18.7°C | 13.1°C | 7.6°C | 25.4°C | 1.2°C | 145 mm | 81% | 0.5 m/s | 4.4 |
| 1983 | 19.0°C | 13.2°C | 7.4°C | 24.3°C | -0.6°C | 124 mm | 80% | 0.5 m/s | — |
| 1982 | 22.2°C | 16.1°C | 10.0°C | 26.9°C | 2.6°C | 90 mm | 79% | 0.4 m/s | — |
| 1981 | 21.1°C | 14.4°C | 7.6°C | 28.6°C | -1.0°C | 78 mm | 74% | 0.5 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 21.2°C with lows near 9.4°C (mean 15.3°C), based on 45 years of NASA POWER data.
May averages 106 mm of rainfall in Harrisburg, a relatively wet time of year. The wettest on record was 221 mm in 1989.
The hottest May reached 33.5°C in 2006. The coldest dipped to -2.4°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.5°C. Daytime highs moved from 20.5°C to 21.9°C and overnight lows from 8.4°C to 10.1°C over the same span.
May is one of the warmer months of the year in Harrisburg and a relatively wet time of year, so plan for around 21.2°C daytime highs and 9.4°C at night.
Not quite — May is the 8th coolest month in Harrisburg, averaging 15.3°C.
For May in Harrisburg, pack light layers you can adjust through the day, with typical highs of 21.2°C and lows of 9.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 78% — quite humid.
Average wind speed in May is 0.5 m/s. The windiest May on record averaged 0.6 m/s (1997).
The wettest May on record was 1989 with 221 mm. On average, May sees 106 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 Harrisburg 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.
