September 17–23
In 5 of the last 5 years, 5+ of those 7 days hit the bar — the most reliable week of the month. Averaged 6.8/7 good days.
How beach days trend across the year
Share of days that clear the beach bar, by month — September highlighted.
Activity by activity
🏖️ Beach Day · September · South Maui (leeward)
Go for it — the odds are strongly in your favor.
87% of days hit the bar — 131 of 150 days across 5 years.
- Avg high
- 84°F
- Avg daily rain
- 0.04 in
- Avg max wind
- 9 mph
My bar for a beach day: ≤0.08 in rain · ≥75°F high · ≤16 mph wind
🥾 Hiking · September · Upcountry (~700m)
Go for it — the odds are strongly in your favor.
96% of days hit the bar — 144 of 150 days across 5 years.
- Avg high
- 79°F
- Avg daily rain
- 0.04 in
- Avg max wind
- 12 mph
My bar for a hiking: ≤0.20 in rain · 64°F–86°F high
September 23–29
In 5 of the last 5 years, 5+ of those 7 days hit the bar — the most reliable week of the month. Averaged 7/7 good days.
🤿 Snorkeling · September · South Maui (leeward)
Go for it — the odds are strongly in your favor.
89% of days hit the bar — 134 of 150 days across 5 years.
- Avg high
- 84°F
- Avg daily rain
- 0.04 in
- Avg max wind
- 9 mph
My bar for a snorkeling: ≤0.12 in rain · ≥75°F high · ≤12 mph wind
September 17–23
In 5 of the last 5 years, 5+ of those 7 days hit the bar — the most reliable week of the month. Averaged 6.8/7 good days.
🚁 Helicopter Tour · September · Kahului
I’d skip it — most days this month miss the mark.
13% of days hit the bar — 19 of 150 days across 5 years.
- Avg high
- 85°F
- Avg daily rain
- 0.01 in
- Avg max wind
- 19 mph
My bar for a helicopter tour: ≤0.04 in rain · ≤16 mph wind
⛵ Boat Tour · September · Māʻalaea Bay
Go for it — the odds are strongly in your favor.
100% of days hit the bar — 150 of 150 days across 5 years.
- Avg high
- 85°F
- Avg daily rain
- 0.00 in
- Avg max wind
- 10 mph
My bar for a boat tour: ≤0.20 in rain · ≤19 mph wind
September 17–23
In 5 of the last 5 years, 5+ of those 7 days hit the bar — the most reliable week of the month. Averaged 7/7 good days.
Can you see whales in Maui in September?
No — the humpbacks are 2,500 miles north this month, feeding off Alaska, and there's a personal story behind why I'm so certain. September is exactly when it happened. In September 2018 I stood on the bluff above Hulopoʻe Bay on Lānaʻi — the island right across the channel from Maui — and watched a single huge fluke rise out of the water. My first whale, I told everyone, for years.
Then I built this tool and learned humpbacks aren't in Hawaii in September at all; they're 2,500 miles north, feeding off Alaska. Whatever I saw, it wasn't the humpback I'd assumed. That gap — between what I was sure I saw and what the data actually allows — is the whole reason this site exists. I stopped trusting one vivid memory and started trusting the record.
And the record is generous about September, just not for whales. Come this month for warm, clear, uncrowded water — not for spouts. If whales are the point, that's a winter trip.
What's the best thing to do in Maui in September?
Snorkeling is the star: an 89% GO, the best reading of the year, thanks to clear, calm late-summer water — best on the September 17–23 window. Boats were a flat 100% GO, also peaking September 17–23 with a perfect 7 out of 7. Beaches matched at 87%, same window. Hiking was a 96% GO, best a little later at September 23–29, a flawless 7/7.
The helicopter is the lone holdout: a 13% SKIP, with the trades over Kahului still up at 31.2 km/h and the best window landing 0 of 5 years. Not yet — give it another month or two.
When should I go if I've only got a few days?
Mid-to-late September is wonderfully easy to time: the snorkel, beach and boat windows all fall on September 17–23 (the boat window perfect), with the hike peaking just after on September 23–29, also perfect. Stack the back half of the month, keep half an eye on the tropics, and skip the helicopter.
Is September a good time to visit Maui?
It's my quiet favorite for a beach-and-snorkel trip. You get essentially summer weather — the clearest water of the year, in fact — with thinner crowds and softer prices than June through August. The honest caveats are no whales and a small, late-season storm risk worth watching.
If those don't apply to you, September is the value pick of the warm half of the year. Weigh it against August (hotter, busier) and October (a touch cooler, with the helicopter starting to come back), and read the numbers under each call before you trust mine.
Going with someone? Send them the call.
Saves the “which month?” back-and-forth.
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