May is close to Hilo's year-round average, with average highs near 23.5°C and lows around 19.4°C (mean 21.5°C). It is one of the drier months, averaging 123 mm of rainfall and 81% relative humidity across the period.
May is close to Hilo's year-round average. Across 45 years of records, the warmest May in Hilo was 1996 — when the month averaged 23.6°C — while the coldest was 1985 at 20.3°C. Typical May days reach 23.5°C with nights near 19.4°C. The long-term May temperature trend is broadly flat.
May is one of the drier months in Hilo, averaging 123 mm of rainfall. The wettest May on record was 2006 with 522 mm, while the driest was 1993 at 2 mm.
Relative humidity in Hilo during May averages 81%. The most humid May was 2002 at 86%, and the least humid was 1993 at 75%.
May receives about 5.9 kWh/m²/day of solar energy in Hilo. The sunniest May was 2003 at 6.6 kWh/m²/day, and the cloudiest were 2002 and 2018 at 5.3.
Average wind speed in Hilo during May is 4.1 m/s. The windiest May was 1998 at 5.4 m/s, while the calmest was 2009 at 3.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 21.1°C | 21.8°C | 21.4°C | 21.5°C | 21.6°C | +0.5°C |
| Avg High | 23.1°C | 24.1°C | 23.5°C | 23.4°C | 23.5°C | +0.4°C |
| Avg Low | 19.1°C | 19.4°C | 19.3°C | 19.6°C | 19.7°C | +0.6°C |
| Avg Rain | 130 mm | 31 mm | 172 mm | 172 mm | 103 mm | -27 mm |
May temperatures in Hilo have risen by about 0.7°C between 1981–1985 and 2021–2025.
May has ranged from a record low of 16.3°C (1987) to a record high of 29.2°C (1997).
Rainfall in May is one of the drier months, averaging 123 mm, with a wettest year of 522 mm.
One of the best times to visit Hilo
May is one of the best times to visit Hilo. Expect days averaging 23.5°C and nights around 19.4°C (mean 21.5°C) — close to Hilo's yearly average — with higher rainfall (123 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 23.7°C | 21.8°C | 19.8°C | 24.7°C | 19.2°C | 86 mm | 81% | 4.2 m/s | 6.1 |
| 2024 | 23.4°C | 21.6°C | 19.7°C | 25.0°C | 18.8°C | 123 mm | 85% | 4.1 m/s | 5.9 |
| 2023 | 23.1°C | 21.3°C | 19.5°C | 24.6°C | 18.8°C | 225 mm | 84% | 3.8 m/s | 5.9 |
| 2022 | 23.5°C | 21.6°C | 19.6°C | 25.5°C | 18.7°C | 81 mm | 83% | 4 m/s | 5.8 |
| 2021 | 23.7°C | 21.6°C | 19.6°C | 26.4°C | 18.6°C | 36 mm | 81% | 4.1 m/s | 6.2 |
| 2020 | 23.8°C | 21.8°C | 19.7°C | 25.6°C | 18.6°C | 67 mm | 82% | 4 m/s | 6.3 |
| 2019 | 24.7°C | 22.4°C | 20.1°C | 26.0°C | 18.1°C | 179 mm | 82% | 3.5 m/s | 6.4 |
| 2018 | 23.7°C | 22.0°C | 20.3°C | 24.9°C | 19.2°C | 119 mm | 86% | 4.1 m/s | 5.3 |
| 2017 | 23.7°C | 21.8°C | 19.9°C | 25.5°C | 19.2°C | 181 mm | 82% | 4 m/s | 6 |
| 2016 | 23.6°C | 21.7°C | 19.8°C | 25.0°C | 19.0°C | 250 mm | 84% | 3.7 m/s | 5.6 |
| 2015 | 23.1°C | 21.3°C | 19.4°C | 25.9°C | 18.6°C | 209 mm | 83% | 3.9 m/s | 5.6 |
| 2014 | 24.0°C | 21.9°C | 19.8°C | 24.8°C | 19.1°C | 118 mm | 82% | 3.7 m/s | 5.6 |
| 2013 | 24.1°C | 22.1°C | 20.0°C | 26.3°C | 18.5°C | 196 mm | 82% | 4 m/s | 5.7 |
| 2012 | 22.3°C | 20.5°C | 18.6°C | 23.9°C | 17.8°C | 78 mm | 81% | 4.4 m/s | 6.1 |
| 2011 | 22.3°C | 20.8°C | 19.3°C | 23.6°C | 18.2°C | 241 mm | 85% | 4.4 m/s | 5.6 |
| 2010 | 22.5°C | 20.8°C | 19.0°C | 23.3°C | 18.5°C | 150 mm | 83% | 4.3 m/s | 6.2 |
| 2009 | 24.3°C | 22.0°C | 19.7°C | 25.7°C | 18.3°C | 77 mm | 83% | 3.2 m/s | 5.8 |
| 2008 | 22.7°C | 20.8°C | 18.8°C | 24.1°C | 18.2°C | 60 mm | 82% | 4.2 m/s | 5.7 |
| 2007 | 22.9°C | 20.9°C | 19.0°C | 24.5°C | 18.6°C | 138 mm | 81% | 4.1 m/s | 6.2 |
| 2006 🌧️ | 22.6°C | 20.8°C | 19.0°C | 24.4°C | 17.9°C | 522 mm | 83% | 4.2 m/s | 5.7 |
| 2005 | 23.8°C | 21.7°C | 19.6°C | 25.5°C | 19.2°C | 71 mm | 81% | 3.8 m/s | 6.2 |
| 2004 | 24.2°C | 22.3°C | 20.5°C | 26.2°C | 19.4°C | 248 mm | 85% | 3.8 m/s | 5.8 |
| 2003 | 23.4°C | 21.2°C | 18.9°C | 25.8°C | 17.8°C | 89 mm | 81% | 3.8 m/s | 6.6 |
| 2002 | 23.4°C | 21.6°C | 19.8°C | 24.8°C | 19.3°C | 462 mm | 86% | 3.7 m/s | 5.3 |
| 2001 | 23.6°C | 21.2°C | 18.8°C | 25.3°C | 17.8°C | 40 mm | 79% | 4.1 m/s | 5.9 |
| 2000 | 23.6°C | 21.2°C | 18.8°C | 24.6°C | 17.9°C | 12 mm | 78% | 4.2 m/s | 6.3 |
| 1999 | 23.0°C | 20.8°C | 18.7°C | 24.1°C | 17.8°C | 69 mm | 78% | 4.3 m/s | 6.1 |
| 1998 | 22.2°C | 20.5°C | 18.7°C | 23.3°C | 17.4°C | 53 mm | 78% | 5.4 m/s | 6 |
| 1997 | 25.4°C | 22.7°C | 20.0°C | 29.2°C | 18.6°C | 17 mm | 77% | 3.7 m/s | 5.7 |
| 1996 🔥 | 26.4°C | 23.6°C | 20.7°C | 28.0°C | 19.1°C | 4 mm | 76% | 3.6 m/s | 6.1 |
| 1995 | 24.4°C | 22.0°C | 19.5°C | 26.7°C | 18.3°C | 4 mm | 77% | 4.5 m/s | 5.8 |
| 1994 | 23.9°C | 21.7°C | 19.4°C | 25.9°C | 18.2°C | 3 mm | 77% | 4.8 m/s | 6.1 |
| 1993 | 24.0°C | 21.6°C | 19.2°C | 25.2°C | 18.4°C | 2 mm | 75% | 4.5 m/s | 6.1 |
| 1992 | 25.5°C | 22.7°C | 19.9°C | 28.0°C | 17.5°C | 11 mm | 76% | 3.5 m/s | 5.8 |
| 1991 | 23.1°C | 21.1°C | 19.1°C | 24.0°C | 17.4°C | 14 mm | 78% | 4.5 m/s | 5.6 |
| 1990 | 22.9°C | 21.0°C | 19.2°C | 24.1°C | 18.1°C | 129 mm | 83% | 4.6 m/s | 5.6 |
| 1989 | 23.7°C | 21.8°C | 19.8°C | 25.1°C | 18.1°C | 74 mm | 81% | 4.4 m/s | 5.6 |
| 1988 | 23.4°C | 21.4°C | 19.4°C | 25.3°C | 18.2°C | 72 mm | 83% | 4.4 m/s | 5.7 |
| 1987 | 23.2°C | 20.9°C | 18.6°C | 25.9°C | 16.3°C | 72 mm | 81% | 3.6 m/s | 5.7 |
| 1986 | 23.2°C | 21.4°C | 19.5°C | 24.9°C | 19.0°C | 52 mm | 83% | 4 m/s | 5.6 |
| 1985 ❄️ | 22.1°C | 20.3°C | 18.6°C | 24.1°C | 17.4°C | 304 mm | 84% | 4.1 m/s | 5.7 |
| 1984 | 22.9°C | 20.9°C | 19.0°C | 24.6°C | 17.8°C | 132 mm | 83% | 4.1 m/s | 5.8 |
| 1983 | 22.2°C | 20.4°C | 18.5°C | 23.5°C | 17.4°C | 236 mm | 83% | 4.2 m/s | — |
| 1982 | 23.2°C | 21.2°C | 19.1°C | 24.8°C | 17.8°C | 173 mm | 82% | 4.1 m/s | — |
| 1981 | 24.0°C | 21.7°C | 19.4°C | 25.7°C | 18.6°C | 59 mm | 78% | 4 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 23.5°C with lows near 19.4°C (mean 21.5°C), based on 45 years of NASA POWER data.
May averages 123 mm of rainfall in Hilo, one of the drier months. The wettest on record was 522 mm in 2006.
The hottest May reached 29.2°C in 1997. The coldest dipped to 16.3°C in 1987.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 0.7°C. Daytime highs moved from 22.9°C to 23.5°C and overnight lows from 18.9°C to 19.6°C over the same span.
May is close to Hilo's year-round average and one of the drier months, so plan for around 23.5°C daytime highs and 19.4°C at night.
Not quite — May is the 6th coolest month in Hilo, averaging 21.5°C.
For May in Hilo, pack light layers you can adjust through the day, with typical highs of 23.5°C and lows of 19.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 81% — quite humid.
Average wind speed in May is 4.1 m/s. The windiest May on record averaged 5.4 m/s (1998).
The wettest May on record was 2006 with 522 mm. On average, May sees 123 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 Hilo 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.
