How I Make the Call
No magic, no AI weatherman. I take 5 years of real daily weather, set a plain bar for what counts as a good day for each thing you might do, and count how often the last 5years cleared it. That’s the whole trick. Here’s every step, in the open — because a call you can’t check isn’t worth much.
The data
Every number comes from Open-Meteo’s historical archive (2021–2025), which is built on the ECMWF/NOAA ERA5 record — the same reanalysis dataset researchers use. It’s free, and I store the exact daily figures so the calls don’t shift under me.
How I score a month
For each activity I count the share of that month’s days (across all 5 years) that cleared the bar, then turn it into one of three calls:
- GO 65%+ of days clear the bar — odds are strongly with you.
- RISK 40–65% — a coin flip. Bookable, but have a plan B.
- SKIPunder 40% — most days miss. I’d pick another month.
The bar for each activity
These bars are my judgment as a former travel PM — not science, not a survey. Shown openly so you can disagree:
| Activity | A good day means |
|---|---|
| 🏖️ Beach Day | ≤0.08 in rain · ≥75°F high · ≤16 mph wind |
| 🥾 Hiking | ≤0.20 in rain · 64°F–86°F high |
| 🤿 Snorkeling | ≤0.12 in rain · ≥75°F high · ≤12 mph wind |
| 🚁 Helicopter Tour | ≤0.04 in rain · ≤16 mph wind |
| ⛵ Boat Tour | ≤0.20 in rain · ≤19 mph wind |
Where I measure (this matters more than you'd think)
Maui isn’t one weather. The central Kahului isthmus is the windiest spot on the island — measure beaches there and summer wrongly looks terrible. So each activity is scored where it actually happens:
| 🏖️ Beach Day | Kīhei / Wailea, South Maui (leeward beaches) |
| 🥾 Hiking | Upcountry Maui — Makawao / Kula (~700m) |
| 🤿 Snorkeling | Kīhei / Wailea, South Maui (leeward beaches) |
| 🚁 Helicopter Tour | Kahului / OGG (central, helicopter departure) |
| ⛵ Boat Tour | Māʻalaea Bay (leeward boat / snorkel-cruise harbor) |
The “safest week” thing
On every month page I also flag the single best 7-day stretch — the run of dates that held up across the most years. If you can pick your week, that’s the one to book.
What this honestly is NOT
- Not a forecast. It can’t tell you about your specific dates — only how often a month usually delivers.
- Not microclimate-perfect. One point per activity can’t capture every cove and valley. Treat it as the regional read.
- Not objective truth. The bars are my taste. Nudge them with the calibration note up top.
- Whale numbers are estimates, not counted sightings — see that page for the caveat.
Questions or think a bar’s wrong? Here’s who’s behind this.
Like the approach? Pass it on.
Honest weather odds, shown openly so you can overrule me.
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