May is close to Halfmoon Bay's year-round average, with average highs near 11.4°C and lows around 8.9°C (mean 10.2°C). It is a relatively wet time of year, averaging 114 mm of rainfall and 84% relative humidity across the period.
May is close to Halfmoon Bay's year-round average. Across 45 years of records, the warmest Mays in Halfmoon Bay were 1999, 2019 and 2022 — when the month averaged 11.9°C — while the coldest was 1992 at 8.1°C. Typical May days reach 11.4°C with nights near 8.9°C. The long-term trend is warming, about 0.3°C per decade.
May is a relatively wet time of year in Halfmoon Bay, averaging 114 mm of rainfall. The wettest May on record was 1982 with 176 mm, while the driest was 2020 at 52 mm.
Relative humidity in Halfmoon Bay during May averages 84%. The most humid May was 2001 at 88%, and the least humid was 2024 at 82%.
May receives about 1.4 kWh/m²/day of solar energy in Halfmoon Bay. The sunniest Mays were 2020, 2021 and 2025, among others at 1.5 kWh/m²/day, and the cloudiest were 1998, 2001 and 2011 at 1.2.
Average wind speed in Halfmoon Bay during May is 4.5 m/s. The windiest Mays were 1990 and 2002 at 5.5 m/s, while the calmest was 1981 at 3.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 9.6°C | 10.0°C | 9.9°C | 10.5°C | 11.0°C | +1.4°C |
| Avg High | 10.9°C | 11.2°C | 11.2°C | 11.7°C | 12.4°C | +1.5°C |
| Avg Low | 8.3°C | 8.8°C | 8.6°C | 9.2°C | 9.7°C | +1.4°C |
| Avg Rain | 116 mm | 116 mm | 126 mm | 112 mm | 92 mm | -24 mm |
May temperatures in Halfmoon Bay have risen by about 1.4°C between 1981–1985 and 2021–2025.
May has ranged from a record low of 3.1°C (1988) to a record high of 18°C (2023).
Rainfall in May is a relatively wet time of year, averaging 114 mm, with a wettest year of 176 mm.
A good time to visit Halfmoon Bay
May is a good time to visit Halfmoon Bay, with days averaging 11.4°C and nights around 8.9°C (mean 10.2°C, close to Halfmoon Bay's yearly average) and higher rainfall. February and March 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 | 13.1°C | 11.7°C | 10.4°C | 17.1°C | 7.3°C | 80 mm | 82% | 5.1 m/s | 1.5 |
| 2024 | 10.3°C | 9.1°C | 8.0°C | 14.8°C | 5.4°C | 78 mm | 82% | 4.5 m/s | 1.4 |
| 2023 | 13.1°C | 11.8°C | 10.5°C | 18.0°C | 6.9°C | 144 mm | 86% | 4.2 m/s | 1.4 |
| 2022 | 13.3°C | 11.9°C | 10.5°C | 16.7°C | 6.8°C | 90 mm | 83% | 4.3 m/s | 1.4 |
| 2021 | 12.0°C | 10.5°C | 9.0°C | 15.9°C | 5.7°C | 107 mm | 83% | 4.4 m/s | 1.5 |
| 2020 | 12.3°C | 11.0°C | 9.7°C | 16.3°C | 6.7°C | 52 mm | 85% | 3.7 m/s | 1.5 |
| 2019 | 13.2°C | 11.9°C | 10.6°C | 16.0°C | 7.0°C | 131 mm | 84% | 4.8 m/s | 1.3 |
| 2018 | 11.1°C | 9.8°C | 8.5°C | 16.0°C | 5.8°C | 94 mm | 83% | 4.7 m/s | 1.4 |
| 2017 | 11.6°C | 10.4°C | 9.1°C | 14.3°C | 6.1°C | 75 mm | 85% | 3.8 m/s | 1.5 |
| 2016 | 12.3°C | 11.1°C | 9.8°C | 16.6°C | 6.0°C | 145 mm | 84% | 4.6 m/s | 1.3 |
| 2015 | 11.6°C | 10.4°C | 9.1°C | 16.6°C | 4.2°C | 90 mm | 82% | 5.3 m/s | 1.3 |
| 2014 | 12.0°C | 10.6°C | 9.3°C | 15.7°C | 5.2°C | 158 mm | 84% | 4.8 m/s | 1.4 |
| 2013 | 11.5°C | 10.3°C | 9.1°C | 14.9°C | 3.9°C | 127 mm | 86% | 4.7 m/s | 1.3 |
| 2012 | 11.5°C | 10.0°C | 8.5°C | 15.1°C | 5.8°C | 116 mm | 84% | 4.1 m/s | 1.4 |
| 2011 | 11.7°C | 10.5°C | 9.2°C | 14.5°C | 6.3°C | 113 mm | 86% | 4.8 m/s | 1.2 |
| 2010 | 10.8°C | 9.7°C | 8.7°C | 14.1°C | 5.8°C | 73 mm | 87% | 3.9 m/s | 1.4 |
| 2009 | 10.1°C | 8.9°C | 7.7°C | 13.4°C | 5.5°C | 160 mm | 85% | 4.2 m/s | 1.4 |
| 2008 | 10.5°C | 9.4°C | 8.4°C | 13.7°C | 5.8°C | 99 mm | 84% | 3.7 m/s | 1.4 |
| 2007 | 12.5°C | 11.2°C | 9.9°C | 14.8°C | 6.9°C | 95 mm | 83% | 5.3 m/s | 1.5 |
| 2006 | 11.3°C | 10.0°C | 8.8°C | 13.4°C | 6.3°C | 95 mm | 85% | 3.6 m/s | 1.5 |
| 2005 | 11.0°C | 9.7°C | 8.4°C | 15.4°C | 5.3°C | 122 mm | 85% | 4.3 m/s | 1.5 |
| 2004 | 10.8°C | 9.6°C | 8.4°C | 14.4°C | 5.8°C | 135 mm | 87% | 4 m/s | 1.4 |
| 2003 | 11.3°C | 9.9°C | 8.5°C | 14.4°C | 5.5°C | 148 mm | 85% | 5.1 m/s | 1.3 |
| 2002 | 11.1°C | 9.8°C | 8.5°C | 14.5°C | 3.5°C | 105 mm | 84% | 5.5 m/s | 1.3 |
| 2001 | 10.5°C | 9.4°C | 8.4°C | 13.9°C | 4.5°C | 136 mm | 88% | 4.4 m/s | 1.2 |
| 2000 | 12.5°C | 10.9°C | 9.3°C | 15.6°C | 5.9°C | 167 mm | 83% | 4.5 m/s | 1.3 |
| 1999 🔥 | 13.1°C | 11.9°C | 10.6°C | 16.6°C | 6.1°C | 114 mm | 83% | 4.9 m/s | 1.4 |
| 1998 | 11.0°C | 9.9°C | 8.7°C | 13.0°C | 5.7°C | 86 mm | 86% | 4.6 m/s | 1.2 |
| 1997 | 11.2°C | 10.1°C | 8.9°C | 14.7°C | 5.6°C | 92 mm | 86% | 4 m/s | 1.4 |
| 1996 | 11.7°C | 10.4°C | 9.0°C | 16.5°C | 5.5°C | 141 mm | 83% | 5.4 m/s | 1.3 |
| 1995 | 12.0°C | 10.7°C | 9.5°C | 16.0°C | 6.4°C | 151 mm | 84% | 4.4 m/s | 1.5 |
| 1994 | 10.9°C | 9.7°C | 8.4°C | 14.9°C | 5.7°C | 148 mm | 85% | 4.5 m/s | 1.5 |
| 1993 | 11.1°C | 9.8°C | 8.5°C | 14.4°C | 6.1°C | 97 mm | 85% | 4.5 m/s | 1.5 |
| 1992 ❄️ | 9.3°C | 8.1°C | 6.8°C | 13.6°C | 3.7°C | 62 mm | 83% | 4.6 m/s | 1.5 |
| 1991 | 10.8°C | 9.7°C | 8.6°C | 12.8°C | 4.9°C | 105 mm | 84% | 5 m/s | 1.4 |
| 1990 | 11.3°C | 10.1°C | 8.9°C | 14.6°C | 6.6°C | 168 mm | 83% | 5.5 m/s | 1.4 |
| 1989 | 10.8°C | 9.6°C | 8.3°C | 13.7°C | 4.8°C | 65 mm | 84% | 4.2 m/s | 1.5 |
| 1988 | 9.5°C | 8.3°C | 7.0°C | 13.7°C | 3.1°C | 149 mm | 84% | 5.1 m/s | 1.3 |
| 1987 | 11.6°C | 10.2°C | 8.8°C | 15.3°C | 6.1°C | 70 mm | 83% | 4.6 m/s | 1.4 |
| 1986 | 11.4°C | 10.0°C | 8.6°C | 14.6°C | 5.7°C | 154 mm | 84% | 4.5 m/s | 1.5 |
| 1985 | 11.3°C | 10.1°C | 8.9°C | 14.8°C | 5.8°C | 112 mm | 85% | 3.8 m/s | 1.5 |
| 1984 | 10.3°C | 9.1°C | 7.8°C | 14.1°C | 4.7°C | 104 mm | 83% | 4.7 m/s | 1.5 |
| 1983 | 9.8°C | 8.5°C | 7.3°C | 12.5°C | 3.7°C | 136 mm | 83% | 4.8 m/s | — |
| 1982 🌧️ | 11.9°C | 10.4°C | 9.0°C | 14.7°C | 5.1°C | 176 mm | 82% | 4.8 m/s | — |
| 1981 | 11.3°C | 10.1°C | 8.9°C | 16.0°C | 6.9°C | 80 mm | 86% | 3.5 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 11.4°C with lows near 8.9°C (mean 10.2°C), based on 45 years of NASA POWER data.
May averages 114 mm of rainfall in Halfmoon Bay, a relatively wet time of year. The wettest on record was 176 mm in 1982.
The hottest May reached 18°C in 2023. The coldest dipped to 3.1°C in 1988.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.4°C. Daytime highs moved from 10.9°C to 12.4°C and overnight lows from 8.4°C to 9.7°C over the same span.
May is close to Halfmoon Bay's year-round average and a relatively wet time of year, so plan for around 11.4°C daytime highs and 8.9°C at night.
Not quite — May is the 6th coolest month in Halfmoon Bay, averaging 10.2°C.
For May in Halfmoon Bay, pack light layers you can adjust through the day, with typical highs of 11.4°C and lows of 8.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 84% — quite humid.
Average wind speed in May is 4.5 m/s. The windiest May on record averaged 5.5 m/s (1990).
The wettest May on record was 1982 with 176 mm. On average, May sees 114 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 Halfmoon Bay 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.
