May is one of the warmer months of the year in Rockford, with average highs near 20.1°C and lows around 8°C (mean 14.1°C). It is a relatively wet time of year, averaging 101 mm of rainfall and 76% relative humidity across the period.
May is one of the warmer months of the year in Rockford. Across 45 years of records, the warmest Mays in Rockford were 1991 and 2018 — when the month averaged 17.2°C — while the coldest was 1997 at 10.8°C. Typical May days reach 20.1°C with nights near 8°C. The long-term trend is warming, about 0.2°C per decade.
May is a relatively wet time of year in Rockford, averaging 101 mm of rainfall. The wettest May on record was 2004 with 229 mm, while the driest was 1992 at 25 mm.
Relative humidity in Rockford during May averages 76%. The most humid May was 2019 at 83%, and the least humid was 1988 at 68%.
May receives about 5.5 kWh/m²/day of solar energy in Rockford. The sunniest May was 1988 at 6.8 kWh/m²/day, and the cloudiest was 1996 at 4.3.
Average wind speed in Rockford during May is 3.2 m/s. The windiest May was 1997 at 3.9 m/s, while the calmest was 2018 at 2.7 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.9°C | 13.7°C | 13.8°C | 14.5°C | 14.4°C | +0.5°C |
| Avg High | 20.1°C | 19.7°C | 19.9°C | 20.4°C | 20.4°C | +0.3°C |
| Avg Low | 7.7°C | 7.7°C | 7.7°C | 8.7°C | 8.4°C | +0.7°C |
| Avg Rain | 85 mm | 99 mm | 113 mm | 115 mm | 85 mm | +0 mm |
May temperatures in Rockford have risen by about 1.2°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -5.4°C (1989) to a record high of 32.4°C (2018).
Rainfall in May is a relatively wet time of year, averaging 101 mm, with a wettest year of 229 mm.
A good time to visit Rockford
May is a good time to visit Rockford, with days averaging 20.1°C and nights around 8°C (mean 14.1°C, warmer than Rockford'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 | 20.0°C | 13.7°C | 7.3°C | 28.4°C | 1.2°C | 67 mm | 73% | 3.1 m/s | 5.8 |
| 2024 | 22.2°C | 15.9°C | 9.6°C | 27.8°C | 5.5°C | 119 mm | 76% | 3.1 m/s | 6 |
| 2023 | 21.2°C | 14.5°C | 7.9°C | 29.0°C | -0.8°C | 45 mm | 70% | 2.8 m/s | 6.3 |
| 2022 | 20.9°C | 15.4°C | 9.9°C | 29.7°C | -0.9°C | 82 mm | 79% | 3.4 m/s | 4.8 |
| 2021 | 19.9°C | 14.1°C | 8.3°C | 28.2°C | 1.0°C | 59 mm | 73% | 3.1 m/s | 5.4 |
| 2020 | 18.3°C | 12.8°C | 7.3°C | 28.1°C | -3.6°C | 139 mm | 81% | 3.1 m/s | 5.5 |
| 2019 | 18.4°C | 12.7°C | 7.1°C | 25.2°C | 1.2°C | 176 mm | 83% | 3.1 m/s | 4.9 |
| 2018 | 23.2°C | 17.2°C | 11.3°C | 32.4°C | 4.7°C | 157 mm | 79% | 2.7 m/s | 5.6 |
| 2017 | 18.5°C | 12.9°C | 7.3°C | 27.4°C | -0.7°C | 112 mm | 80% | 3.3 m/s | 5.5 |
| 2016 | 20.1°C | 14.2°C | 8.3°C | 27.0°C | -2.0°C | 89 mm | 76% | 3 m/s | 5.9 |
| 2015 | 21.0°C | 15.1°C | 9.2°C | 26.8°C | 1.4°C | 120 mm | 76% | 3.5 m/s | 5.3 |
| 2014 | 20.2°C | 14.1°C | 7.9°C | 28.5°C | 1.9°C | 101 mm | 77% | 3.1 m/s | 5.7 |
| 2013 | 20.4°C | 14.6°C | 8.9°C | 27.9°C | -0.5°C | 111 mm | 80% | 3.1 m/s | 5.5 |
| 2012 | 22.7°C | 16.4°C | 10.1°C | 31.6°C | 4.2°C | 76 mm | 73% | 3.2 m/s | 6.2 |
| 2011 | 18.9°C | 13.3°C | 7.7°C | 29.8°C | -1.8°C | 94 mm | 81% | 3.5 m/s | 5.2 |
| 2010 | 20.5°C | 14.9°C | 9.4°C | 29.8°C | -0.8°C | 118 mm | 77% | 3.2 m/s | 5.7 |
| 2009 | 19.5°C | 13.4°C | 7.4°C | 26.4°C | -0.2°C | 85 mm | 77% | 3.3 m/s | 5.8 |
| 2008 | 18.2°C | 11.9°C | 5.5°C | 25.1°C | 0.1°C | 87 mm | 77% | 3.4 m/s | 5.7 |
| 2007 | 22.3°C | 15.9°C | 9.5°C | 28.4°C | 3.6°C | 44 mm | 74% | 3.5 m/s | 6 |
| 2006 | 20.0°C | 14.5°C | 9.0°C | 30.6°C | 1.2°C | 108 mm | 78% | 3.1 m/s | 5.3 |
| 2005 | 19.3°C | 13.1°C | 7.0°C | 26.1°C | -2.2°C | 68 mm | 71% | 3.3 m/s | 5.5 |
| 2004 🌧️ | 20.6°C | 14.4°C | 8.2°C | 27.8°C | -1.1°C | 229 mm | 81% | 3.3 m/s | 5 |
| 2003 | 19.5°C | 13.0°C | 6.6°C | 24.8°C | 0.0°C | 120 mm | 73% | 3.6 m/s | 5.5 |
| 2002 | 17.9°C | 11.7°C | 5.4°C | 26.9°C | -1.8°C | 78 mm | 76% | 3.5 m/s | 5.6 |
| 2001 | 20.4°C | 14.6°C | 8.9°C | 28.6°C | 2.9°C | 121 mm | 76% | 3.2 m/s | 5.4 |
| 2000 | 21.7°C | 15.5°C | 9.3°C | 27.9°C | 1.9°C | 193 mm | 75% | 3.3 m/s | 4.8 |
| 1999 | 21.2°C | 15.4°C | 9.5°C | 27.3°C | 3.7°C | 102 mm | 77% | 3.5 m/s | 5.7 |
| 1998 | 22.6°C | 16.6°C | 10.7°C | 28.6°C | 5.3°C | 122 mm | 78% | 3 m/s | 6 |
| 1997 ❄️ | 17.3°C | 10.8°C | 4.3°C | 25.2°C | -0.4°C | 92 mm | 73% | 3.9 m/s | 5.6 |
| 1996 | 17.3°C | 11.6°C | 5.9°C | 29.1°C | 0.2°C | 180 mm | 79% | 3.3 m/s | 4.3 |
| 1995 | 18.7°C | 13.1°C | 7.5°C | 24.9°C | 1.7°C | 126 mm | 76% | 3.3 m/s | 5.2 |
| 1994 | 20.2°C | 13.3°C | 6.5°C | 27.9°C | -0.3°C | 29 mm | 71% | 2.8 m/s | 6.5 |
| 1993 | 19.7°C | 14.0°C | 8.3°C | 26.0°C | 0.9°C | 75 mm | 80% | 3.3 m/s | 4.9 |
| 1992 | 19.7°C | 13.0°C | 6.3°C | 26.8°C | -1.7°C | 25 mm | 71% | 2.8 m/s | 6.3 |
| 1991 🔥 | 22.2°C | 17.2°C | 12.2°C | 29.7°C | 1.7°C | 100 mm | 83% | 3.1 m/s | 4.6 |
| 1990 | 17.7°C | 11.8°C | 5.9°C | 23.7°C | -0.8°C | 138 mm | 76% | 3.5 m/s | 5.1 |
| 1989 | 19.5°C | 13.0°C | 6.4°C | 28.0°C | -5.4°C | 62 mm | 70% | 3.1 m/s | 5.8 |
| 1988 | 21.8°C | 14.6°C | 7.5°C | 28.8°C | 0.3°C | 30 mm | 68% | 3.1 m/s | 6.8 |
| 1987 | 22.3°C | 16.1°C | 9.8°C | 27.7°C | 1.0°C | 111 mm | 77% | 3.2 m/s | 5.8 |
| 1986 | 20.2°C | 14.3°C | 8.4°C | 28.4°C | -0.7°C | 100 mm | 78% | 3.2 m/s | 5.1 |
| 1985 | 21.2°C | 15.0°C | 8.8°C | 27.9°C | 1.3°C | 78 mm | 74% | 3.6 m/s | 6.2 |
| 1984 | 18.1°C | 12.0°C | 6.0°C | 25.4°C | 0.3°C | 108 mm | 75% | 3.5 m/s | 5.2 |
| 1983 | 17.0°C | 11.2°C | 5.4°C | 22.8°C | -2.6°C | 117 mm | 80% | 3.4 m/s | — |
| 1982 | 22.4°C | 16.8°C | 11.2°C | 27.1°C | 5.3°C | 107 mm | 81% | 2.9 m/s | — |
| 1981 | 18.8°C | 12.3°C | 5.9°C | 26.7°C | -1.3°C | 50 mm | 70% | 3.3 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 20.1°C with lows near 8°C (mean 14.1°C), based on 45 years of NASA POWER data.
May averages 101 mm of rainfall in Rockford, a relatively wet time of year. The wettest on record was 229 mm in 2004.
The hottest May reached 32.4°C in 2018. The coldest dipped to -5.4°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.2°C. Daytime highs moved from 19.5°C to 20.8°C and overnight lows from 7.5°C to 8.6°C over the same span.
May is one of the warmer months of the year in Rockford and a relatively wet time of year, so plan for around 20.1°C daytime highs and 8°C at night.
Not quite — May is the 8th coolest month in Rockford, averaging 14.1°C.
For May in Rockford, pack light layers you can adjust through the day, with typical highs of 20.1°C and lows of 8°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 76% — quite humid.
Average wind speed in May is 3.2 m/s. The windiest May on record averaged 3.9 m/s (1997).
The wettest May on record was 2004 with 229 mm. On average, May sees 101 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 Rockford 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.
