Andaman Sea Conditions by Month: How Rough Is the Ferry Ride?
The short answer: the Andaman ferry crossing is a comfort question, not a safety question. Ferries simply don’t sail when conditions are unsafe — the harbour master closes the port. What changes through the year is how the crossing feels, and the pattern is strong enough to plan around: February to April is near-flat, June to September is the bumpy season, and December — peak tourist season — is not actually the calmest water of the year.
This page puts numbers on that pattern: ten years of daily wave heights in the seas around the islands, cross-checked against what the fleet actually does each month. It’s the data behind the seasonal advice on our best time to visit and monthly guides.
Sea state by month
Wave heights below are ten years (2015–2024) of daily maximums from a global wave model, for the sea area around Port Blair, Havelock and Neil. Read them as regional open-water conditions, not as the exact sea inside the channels — the islands shelter the crossings, which run calmer than these figures, especially during the southwest monsoon. What the numbers are good for is comparing one month against another, and that comparison is reliable. “Sea state” uses the IMD’s official vocabulary: slight (under 1.25 m), moderate (1.25–2.5 m), rough (over 2.5 m).
| Month | Typical sea | Median daily max | Days reaching “moderate” | The crossing, honestly |
|---|---|---|---|---|
| January | Slight | 0.78 m | 7% | Comfortable; occasional leftover chop early month |
| February | Slight | 0.73 m | 5% | Very calm — the quiet start of the glass window |
| March | Glass | 0.57 m | 1% | Flattest water of the year |
| April | Glass | 0.56 m | 3% | Flattest water of the year |
| May | Mostly slight | 0.91 m | 32% | Fine most days, but pre-monsoon systems can bring the year’s biggest single-day seas |
| June | Slight–moderate | 1.45 m | 66% | Monsoon arrives; swell on the open stretches |
| July | Moderate spells | 1.55 m | 72% | The bumpiest month — and the thinnest timetable |
| August | Slight–moderate | 1.49 m | 68% | Gradual easing, still lively |
| September | Slight–moderate | 1.30 m | 54% | Sea easing; schedules already rebuilding |
| October | Slight | 0.85 m | 22% | Transition month; occasional swell from distant systems |
| November | Slight | 0.77 m | 11% | Settled; full winter timetable |
| December | Slight, some moderate days | 0.89 m | 21% | Peak season, good sailing — but not the year’s calmest |
Three things in that table surprise most people:
Peak season isn’t the calmest sea. December carries the tail of the northeast monsoon — a modest share of days touch “moderate.” The genuinely flat months are February to April, after the crowds thin out. If a mirror-calm crossing matters to you more than the Christmas atmosphere, travel late-season.
July is a schedule story, not a survival story. July is roughly three times rougher than March — that ratio is the solid finding, and it holds across every dataset we checked. But rougher water is not the thing that actually disrupts a July trip. What changes is the timetable: the network drops from about 35 scheduled departures a day in December to 11 in July, operators consolidate to their biggest hulls, and ITT Majestic suspends entirely for July–August. Fewer, bigger, fuller boats — that’s monsoon reality. Details in the ferry schedule guide.
May is the wildcard, not June. The pre-monsoon weeks are calm most days but own the largest single-day seas in the record — this is the Bay of Bengal’s spring cyclone window (Cyclone Mocha, May 2023, sits in this data). A May booking is fine; just treat a cyclone advisory seriously if one appears.
Not all crossings are equal
The three legs feel different, and the difference is geography:
- Havelock ↔ Neil is the most open-water leg — most exposed to the Andaman Sea, and the first to feel monsoon swell. In June–September, prone travellers should take this one in the morning and prefer the larger catamarans.
- Port Blair ↔ Havelock is the main channel: partly sheltered, moderate exposure mid-crossing.
- Port Blair → Baratang (from 1 October 2026) runs through inner straits — the most sheltered water in the network. Its season, 1 October to 15 June, brackets the calm months almost exactly: the timetable is shaped by the sea.
Within any leg, two rules hold year-round: morning sailings are calmer than afternoon ones (the sea breeze builds after midday), and midship seats move least. The full comfort playbook — seats, medication, operator choice — is in the seasickness guide.
About those “four-metre swells”
You’ll see monsoon seas here described as three to four metres, and in the open Bay of Bengal west of the islands that is entirely real — our data records days above four metres, and one December above five. But that is not the water a ferry crosses. The routes run on the eastern, sheltered side of the island chain, and the Andamans take the southwest monsoon on the chin so the channels don’t have to. The number is true of the sea; it is not true of your crossing.
When a cyclone is in the neighbourhood
This is the part that catches travellers out, and it works the opposite way to intuition.
A storm doesn’t have to come near you to cost you a crossing. We checked the wave record on the channels for every tropical system that passed within 500 km of Port Blair since 2021, and nearly all of them lifted the sea above that month’s normal range — including ones several hundred kilometres away that never touched the islands at all.
But you can’t read the risk off a map. The closest cyclone in recent years, Midhili, passed 28 km from Port Blair in November 2023 and produced moderate seas. Mocha, in May 2023, stayed 460 km away and produced the roughest water in the record. Hamoon, a stronger storm at almost exactly Mocha’s distance, did nothing measurable in the channels at all. What matters is where the storm’s fetch is aimed, not how close it gets — so a distant system can matter more than a near one.
And the channels stay calmer than the open sea throughout. Even when a cyclone puts genuinely big water into the Bay of Bengal west of the islands, the sheltered crossings on the eastern side see a fraction of it. That’s the useful thing to understand about cancellations: sailings are stopped by advisories and wind, not by monstrous seas in the channel. The port takes the cautious call well before conditions get anywhere near dangerous, which is exactly what you’d want.
Cyclone season here is not the monsoon, incidentally — it’s October to December, with a smaller spring peak in April and May. Our sister site has the full 35-year storm record in its Andaman cyclone season data.
What a cancellation actually looks like
A handful of days a year — almost all June–September, occasionally around a cyclone advisory in May or October–November — the harbour closes and sailings are cancelled wholesale. When that happens:
- Operators reschedule you to the next available sailing or refund the fare — see the cancellation policy for each operator’s terms.
- Cancellations are decided by the port authorities on IMD/INCOIS advisories, not by individual operators — no company “risks it.”
- Build one buffer day between your last Havelock/Neil sailing and your flight out of Port Blair in monsoon months. That single piece of planning absorbs nearly all cancellation risk.
For today’s conditions, INCOIS publishes a live ocean state forecast for Andaman waters.
FAQ: Sea Conditions in the Andamans
Is the sea rough in the Andamans during monsoon?
Rougher, not rough. June–September brings swell and lively crossings, July most of all — the regional sea runs about three times higher than in March. The sheltered channels the ferries use are calmer than that, and the bigger monsoon effect is the timetable anyway: about a third of the December schedule runs in July.
Which month has the calmest sea for the Andaman ferry?
March and April, with February close behind. The water is at its flattest after peak season ends — December’s northeast-monsoon tail means peak season is pleasant but not glassy.
Do Andaman ferries get cancelled often?
No. Weather cancellations cluster in a handful of monsoon days and cyclone advisories. Port authorities make the call network-wide on IMD guidance, operators rebook or refund, and a one-day buffer before your return flight covers the residual risk.
Does a cyclone nearby mean my ferry is cancelled?
Often, but not because the sea gets dangerous. Nearly every storm passing within 500 km since 2021 lifted channel waves above their normal range, yet even the strongest left the corridors around 2.5 m — moderate, not rough. Sailings stop on port advisories and wind well before conditions get severe. Distance is a poor guide: a storm 460 km away once produced rougher water than one that passed 28 km from Port Blair.
Which ferry route is the roughest?
Havelock ↔ Neil — it’s the most exposed to open sea and feels monsoon swell first. Morning departures and bigger vessels smooth it considerably. The new Port Blair → Baratang route is the opposite extreme: inner-strait water, the calmest in the network.
Is the ferry safe for children and older travellers?
Yes, year-round — sailings only run when the port deems conditions safe. For comfort in June–September, pick morning departures, midship seats, and the larger catamarans, and read our seasickness guide before travelling with anyone prone to motion sickness.
Methodology and its limits. Wave figures are computed from NOAA’s WAVEWATCH III global wave model (variable: significant wave height of combined wind waves and swell), hourly data for 2015–2024, reduced to a daily maximum per IST day and then to monthly statistics — 346,752 hourly readings in total. The model grid is about 55 km, which is too coarse to resolve the individual channels: it reads the region as open water and therefore overstates what a sheltered crossing feels like, most of all in the southwest monsoon. We publish it anyway, clearly labelled, because the month-to-month comparison is robust and the alternative is the vague folklore this page exists to replace. The per-route differences described above are argued from geography and operator experience, not from this model, which cannot see them. Sea-state categories follow the India Meteorological Department scale. Schedule and fleet figures come from our own open ferry dataset, logged from live operator inventory. Storm dates are cross-checked against NOAA’s IBTrACS best-track archive. Data: NOAA/NCEP WAVEWATCH III, a US Government work in the public domain. Full monthly figures: download the CSV.
Published July 2026. Sea-state pattern verified against ten years of reanalysis, IMD classifications, and the operating calendar of all four private operators.