ERA5 almanac comparison — 8 years of real data
Phoenix vs San Juan Islands: weather in May
Phoenix is the clear winner for sun in May: 95% of days historically clear versus just 3% in San Juan Islands — a 92-point gap across 8 years of ERA5 data. This isn't close.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific May. For this
week’s actual forecast, each destination links to its live page below.
Phoenix
AZ
- Clear days, May
- 95%
- Sample size
- n=248 days
- Avg high
- 96°F
- Early May (1st–15th)
- 92%
- Late May (16th–end)
- 97%
- Rain frequency
- 2% of days
San Juan Islands
WA
- Clear days, May
- 3%
- Sample size
- n=248 days
- Avg high
- 61°F
- Early May (1st–15th)
- 4%
- Late May (16th–end)
- 2%
Compare Phoenix vs San Juan Islands in another month
All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.