May is one of the warmer months of the year in Johnstown, with average highs near 19.7°C and lows around 8.3°C (mean 14°C). It is a relatively wet time of year, averaging 106 mm of rainfall and 79% relative humidity across the period.
May is one of the warmer months of the year in Johnstown. Across 45 years of records, the warmest May in Johnstown was 2018 — when the month averaged 17.8°C — while the coldest was 1997 at 10.4°C. Typical May days reach 19.7°C with nights near 8.3°C. The long-term trend is warming, about 0.4°C per decade.
May is a relatively wet time of year in Johnstown, averaging 106 mm of rainfall. The wettest May on record was 2025 with 216 mm, while the driest was 2023 at 44 mm.
Relative humidity in Johnstown during May averages 79%. The most humid Mays were 2011 and 2018 at 85%, and the least humid was 2023 at 71%.
May receives about 5.2 kWh/m²/day of solar energy in Johnstown. The sunniest May was 2007 at 6.5 kWh/m²/day, and the cloudiest was 2003 at 3.9.
Average wind speed in Johnstown during May is 0.1 m/s. The windiest Mays were 2022, 2023 and 2024, among others at 0.1 m/s, while the calmest were 2019, 2020 and 2025, among others at 0 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.4°C | 13.3°C | 13.8°C | 15.5°C | 14.0°C | +0.6°C |
| Avg High | 19.2°C | 19.1°C | 19.7°C | 21.0°C | 19.6°C | +0.4°C |
| Avg Low | 7.6°C | 7.6°C | 8.0°C | 10.1°C | 8.4°C | +0.8°C |
| Avg Rain | 116 mm | 89 mm | 100 mm | 116 mm | 113 mm | -3 mm |
May temperatures in Johnstown have risen by about 1.3°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -4.9°C (2020) to a record high of 32.9°C (2006).
Rainfall in May is a relatively wet time of year, averaging 106 mm, with a wettest year of 216 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.3°C per decade while lows rose 0.5°C per decade, narrowing the gap between day and night.
A good time to visit Johnstown
May is a good time to visit Johnstown, with days averaging 19.7°C and nights around 8.3°C (mean 14°C, warmer than Johnstown's yearly average) and higher rainfall. July and August 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 🌧️ | 19.3°C | 14.2°C | 9.0°C | 26.3°C | 1.4°C | 216 mm | 82% | 0 m/s | 4.5 |
| 2024 | 21.5°C | 16.4°C | 11.4°C | 27.5°C | 3.9°C | 118 mm | 82% | 0.1 m/s | 5.2 |
| 2023 | 19.6°C | 13.1°C | 6.6°C | 26.9°C | 0.4°C | 44 mm | 71% | 0.1 m/s | 6.2 |
| 2022 | 20.8°C | 15.1°C | 9.4°C | 28.3°C | 0.0°C | 145 mm | 80% | 0.1 m/s | 5.3 |
| 2021 | 19.1°C | 13.2°C | 7.3°C | 28.0°C | -1.0°C | 104 mm | 75% | 0.1 m/s | 5.3 |
| 2020 | 17.4°C | 12.1°C | 6.8°C | 27.1°C | -4.9°C | 52 mm | 79% | 0 m/s | 5.2 |
| 2019 | 21.2°C | 16.1°C | 10.9°C | 26.7°C | 2.2°C | 157 mm | 84% | 0 m/s | 4.9 |
| 2018 🔥 | 23.1°C | 17.8°C | 12.5°C | 28.6°C | 2.8°C | 121 mm | 85% | 0 m/s | 5.1 |
| 2017 | 18.7°C | 13.5°C | 8.3°C | 26.9°C | -3.0°C | 154 mm | 80% | 0.1 m/s | 4.7 |
| 2016 | 19.1°C | 13.8°C | 8.6°C | 28.8°C | 0.8°C | 91 mm | 80% | 0.1 m/s | 4.9 |
| 2015 | 22.9°C | 16.9°C | 11.0°C | 27.7°C | 0.9°C | 56 mm | 77% | 0.1 m/s | 5.9 |
| 2014 | 19.8°C | 14.2°C | 8.7°C | 25.8°C | 0.7°C | 109 mm | 80% | 0.1 m/s | 5.2 |
| 2013 | 20.1°C | 14.3°C | 8.6°C | 28.1°C | -1.0°C | 68 mm | 78% | 0 m/s | 5.6 |
| 2012 | 23.0°C | 17.5°C | 12.0°C | 30.6°C | 1.9°C | 144 mm | 80% | 0.1 m/s | 5.4 |
| 2011 | 20.7°C | 15.8°C | 10.9°C | 28.8°C | 1.2°C | 129 mm | 85% | 0 m/s | 4.8 |
| 2010 | 21.0°C | 15.3°C | 9.7°C | 28.3°C | -2.0°C | 127 mm | 80% | 0.1 m/s | 5.2 |
| 2009 | 19.4°C | 14.0°C | 8.5°C | 25.8°C | -1.3°C | 116 mm | 78% | 0.1 m/s | 5.1 |
| 2008 | 17.7°C | 12.0°C | 6.4°C | 25.2°C | 1.1°C | 135 mm | 79% | 0.1 m/s | 5.1 |
| 2007 | 22.1°C | 15.3°C | 8.5°C | 30.1°C | 1.1°C | 52 mm | 73% | 0.1 m/s | 6.5 |
| 2006 | 19.2°C | 13.2°C | 7.3°C | 32.9°C | -0.7°C | 72 mm | 77% | 0.1 m/s | 5.4 |
| 2005 | 17.4°C | 11.6°C | 5.8°C | 25.0°C | -0.3°C | 52 mm | 77% | 0.1 m/s | 5.4 |
| 2004 | 22.7°C | 17.0°C | 11.3°C | 27.0°C | -0.7°C | 128 mm | 82% | 0 m/s | 5.3 |
| 2003 | 17.5°C | 12.7°C | 7.9°C | 23.9°C | 2.8°C | 147 mm | 84% | 0 m/s | 3.9 |
| 2002 | 19.1°C | 12.8°C | 6.5°C | 26.1°C | -3.4°C | 134 mm | 76% | 0.1 m/s | 5.3 |
| 2001 | 20.5°C | 14.3°C | 8.1°C | 27.6°C | 0.9°C | 67 mm | 71% | 0.1 m/s | 5.4 |
| 2000 | 21.2°C | 15.3°C | 9.4°C | 27.1°C | 2.8°C | 99 mm | 78% | 0.1 m/s | 5.2 |
| 1999 | 21.1°C | 14.6°C | 8.1°C | 28.3°C | 2.8°C | 50 mm | 72% | 0.1 m/s | 6.2 |
| 1998 | 21.1°C | 15.9°C | 10.7°C | 28.0°C | 4.7°C | 105 mm | 81% | 0.1 m/s | 5.6 |
| 1997 ❄️ | 16.3°C | 10.4°C | 4.6°C | 24.8°C | -0.5°C | 123 mm | 75% | 0 m/s | 5.6 |
| 1996 | 18.0°C | 12.6°C | 7.2°C | 27.0°C | -2.7°C | 109 mm | 82% | 0.1 m/s | 4.6 |
| 1995 | 18.8°C | 13.2°C | 7.5°C | 24.1°C | -0.9°C | 116 mm | 78% | 0.1 m/s | 5.1 |
| 1994 | 17.2°C | 11.0°C | 4.8°C | 25.3°C | -1.2°C | 77 mm | 78% | 0.1 m/s | 5.2 |
| 1993 | 19.9°C | 13.9°C | 7.9°C | 27.2°C | 1.3°C | 53 mm | 78% | 0.1 m/s | 5.6 |
| 1992 | 18.7°C | 12.7°C | 6.6°C | 25.7°C | 0.3°C | 63 mm | 76% | 0.1 m/s | 5.2 |
| 1991 | 22.7°C | 17.2°C | 11.6°C | 28.3°C | 3.3°C | 50 mm | 80% | 0.1 m/s | 5.8 |
| 1990 | 17.3°C | 11.9°C | 6.6°C | 23.4°C | 1.8°C | 142 mm | 79% | 0.1 m/s | 4.6 |
| 1989 | 17.1°C | 12.2°C | 7.2°C | 25.7°C | 0.5°C | 172 mm | 84% | 0 m/s | 4 |
| 1988 | 19.9°C | 14.1°C | 8.2°C | 27.0°C | 0.3°C | 125 mm | 78% | 0.1 m/s | 5.4 |
| 1987 | 20.9°C | 14.6°C | 8.4°C | 28.2°C | -1.6°C | 94 mm | 80% | 0.1 m/s | 5.6 |
| 1986 | 20.0°C | 14.2°C | 8.3°C | 26.3°C | -2.9°C | 66 mm | 79% | 0.1 m/s | 5.5 |
| 1985 | 20.0°C | 14.0°C | 8.1°C | 25.5°C | -1.0°C | 136 mm | 80% | 0 m/s | 5.6 |
| 1984 | 16.7°C | 11.6°C | 6.5°C | 25.3°C | -1.5°C | 127 mm | 81% | 0 m/s | 4.1 |
| 1983 | 17.6°C | 11.6°C | 5.7°C | 23.1°C | -3.7°C | 133 mm | 80% | 0 m/s | — |
| 1982 | 21.8°C | 15.7°C | 9.6°C | 26.5°C | 1.7°C | 110 mm | 79% | 0.1 m/s | — |
| 1981 | 18.9°C | 12.6°C | 6.3°C | 25.1°C | -2.9°C | 85 mm | 76% | 0.1 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 19.7°C with lows near 8.3°C (mean 14°C), based on 45 years of NASA POWER data.
May averages 106 mm of rainfall in Johnstown, a relatively wet time of year. The wettest on record was 216 mm in 2025.
The hottest May reached 32.9°C in 2006. The coldest dipped to -4.9°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.3°C. Daytime highs moved from 19°C to 20.1°C and overnight lows from 7.2°C to 8.7°C over the same span.
May is one of the warmer months of the year in Johnstown and a relatively wet time of year, so plan for around 19.7°C daytime highs and 8.3°C at night.
Not quite — May is the 8th coolest month in Johnstown, averaging 14°C.
For May in Johnstown, pack light layers you can adjust through the day, with typical highs of 19.7°C and lows of 8.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 79% — quite humid.
Average wind speed in May is 0.1 m/s. The windiest May on record averaged 0.1 m/s (1981).
The wettest May on record was 2025 with 216 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 Johnstown 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.
