Saleh Bay weather: wind, rain and what cancels a whale shark boat

By Saleh Bay Whale Shark Editorial Desk

Saleh Bay weather follows two monsoons: a wet northwest monsoon from December to February and a windier, drier southeast monsoon from June to August, according to an IUCN factsheet. SB Excursions, an operator, calls January and February the roughest. Sea surface readings run warm, and a strong storm can stop boats for several days.

How do the monsoons shape Saleh Bay weather?

The IUCN shark specialist group factsheet gives the plainest account. The northwest monsoon from December to February brings low-speed winds and high rainfall. The southeast monsoon from June to August brings high-speed winds and lower rainfall. Island-wide, Wikivoyage describes Sumbawa's dry season as April to November, with dust and strong winds blown in off the ocean, though that is a community guide speaking for the whole island.

The shape of the bay matters too. The factsheet describes a semi-enclosed embayment connected to the Flores Sea, with small islands, coral reefs, seagrass and mangroves. The BBC goes further, describing a cove that is almost fully enclosed, with a narrow channel drawing in cool, rich water from the deep ocean. The factsheet attributes the bay's productivity to river inputs all year and seasonal upwellings produced by monsoon winds. Shark timing is treated separately on the Saleh Bay whale shark season page.

This page gives no month-by-month rainfall or wind table, because we know of no verified one for the bay itself. The Saleh Bay monsoon pattern above and the operator months below are what is on record. For a live forecast, use a marine weather service close to your dates. The Saleh Bay whale shark overview covers the rest of a trip.

Which months bring cancellations?

All the advice on cancellations comes from companies or travel writers, and none of it comes with a record of cancelled trips.

The three broadly agree that the Saleh Bay rainy season is the riskier period, and they disagree around the edges. November and April are the months where advice splits, so anyone travelling then should have spare days. The blog's account is a useful correction to the idea that the wet season shuts everything: on its description, trips continue on most days and the risk is a cancelled morning, not a closed season.

A cancellation hits harder here than on a short trip because of how long it takes to reach the bay. If you have only one possible morning, any month carries the risk of a wasted journey. Ask for the weather cancellation terms in writing: who decides, by what hour, and what you get back.

Why do wind data and operator advice differ?

Put the factsheet and the operators side by side and they do not obviously fit. The factsheet gives high-speed winds in June to August, right in the middle of the months SB Excursions calls calmest and The Langkah Travel calls ideal. It gives low-speed winds in December to February, overlapping the months SB Excursions calls roughest.

There are some possible explanations, though we cannot prove any of them. A seasonal wind speed may not describe conditions at the hour boats run, and the operators' claims are about crossings in small boats. Rain squalls and short storms may trouble a small open boat in a way an average wind figure does not capture. Shelter also depends on direction in a bay this enclosed. And operators have an interest in selling the months they run most.

Fishers offer a third view that sits closer to the operators. In interviews reported by a 2021 study, they said the wet western season brings rain and strong winds, and that their bagan move from the east of the bay to the west to find shelter around islands. So people who work the water describe strong wind in a season the factsheet lists as low-speed. Our advice is to treat the month tables as rough guides to Saleh Bay sea conditions, and to trust a forecast for your dates over any of them.

How warm is the water?

Warm at the surface, on every measurement cited here. These figures cover different periods and methods, so they are kept separate here.

No measured series for June to August appears in the sources, so July water temperature is an open question beyond the factsheet's wide range, which runs from about 77 to 91°F. The BBC's mention of cool water drawn in from the deep is a reminder that surface readings describe only the top layer. The 2021 study recorded seabed depths of 36 to 81.5 metres at its trip coordinates, and the 2025 paper gives a maximum for the bay of 400 metres. Those are seabed figures, far below the zone where snorkellers meet sharks at a net, and they should not be read as the depth you will be swimming in.

Rain may change how the water looks. SB Excursions says wetter months push more runoff and plankton into the bay and make the water greener. That is an operator's qualitative observation, and no source gives visibility in metres. The 2025 paper reports chlorophyll-a of 0.20 to 3.45 mg/m3 at its sightings, with observations from 05:00 to 09:00, which shows how far productivity varied across those sightings without telling you what you would see through a mask. For the record on what visitors have reported, see the page on Saleh Bay whale shark sightings.

What happens in a storm?

The clearest documented case is from early 2025. Antara reported that during a storm linked to a tropical cyclone seed on 2 to 3 February 2025, dozens of bagan sheltered at Rak Island, and there was no chance of a viewing trip for several days. For a visitor, the lost days are the problem. Anyone on a two-night plan that week could have gone home without a boat.

A storm can cancel a trip in two ways. Small boats may not go out, and the platforms that visitor boats head for may have moved to shelter. So even after the sky clears, the fleet may take time to return to where it was working. This is our inference from the Antara report and the fishers' account of moving for shelter, and no source measures how long that recovery takes.

Three things reduce the risk to your plans: extra days at the end of the trip, flights that can be changed, and written terms for what happens if the boat does not go. None of them guarantees a trip.

What do people ask about the weather in Saleh Bay?

What is the weather like in Saleh Bay?

An IUCN factsheet describes a northwest monsoon from December to February with high rainfall and low-speed winds, and a southeast monsoon from June to August with high-speed winds and lower rainfall. Sea surface temperatures are warm in every measurement cited here.

Which months are roughest in Saleh Bay?

SB Excursions, an operator, calls January and February the roughest. The Langkah Travel advises avoiding January to March. A travel blog says tours still run on most days from December to April, though crossings can be cancelled.

What is the water temperature in Saleh Bay?

An IUCN factsheet gives about 25 to 33°C. A 2021 study measured 29 to 32°C on trips between November and January, and a 2025 paper reports 29.47 to 33.85°C at sightings from February to April 2024.

Do Saleh Bay whale shark boats get cancelled?

Yes. SB Excursions and a travel blog mention cancellations, mostly in the wet months. Antara reported several days without a viewing trip after a storm in February 2025. Ask for the weather cancellation terms in writing before you pay.

Does rain affect visibility in Saleh Bay?

SB Excursions, an operator, says wetter months push more runoff and plankton into the bay and make the water greener. This is a qualitative description only. The sources give no visibility figure in metres for the bay.

Which sources support this page?

• IUCN shark specialist group factsheet: Saleh Bay
• Wikivoyage: Sumbawa
• BBC Future: the giant shark that seems to appear from nowhere
• SB Excursions: Sumbawa whale shark season (operator)
• The Langkah Travel: Saleh Bay guide (operator)
• My Best Places to Visit: Saleh Bay whale sharks (travel blog)
• 2021 IOP study on Saleh Bay whale sharks
• Technical Geography 2025 paper on Saleh Bay
• Antara: whale sharks and people in Saleh Bay

How do I reach the desk?

The desk does not forecast the sea, and it cannot promise that a boat will go on any date. If you want help comparing how providers handle weather cancellations, send your dates and spare days. Requests can turn into paid bookings, giving us a commercial interest. Refund and rebooking terms mean something only when a written offer spells them out. WhatsApp +62 811-3941-4563 or email bd@juaraholding.com.