Best Time to Visit the Great Barrier Reef: Weather by Month & Stinger Season

How the reef changes through the year

The reef has two seasons rather than four. From about May to October the south-east trade winds blow, the air is dry and the sky over Cairns is often clear: rain falls on only five to seven days a month from June to October. The trade winds are strongest from about April to August, when afternoon winds at Green Island average more than 32 km/h, and they ease through September and October. From November the winds drop away, the heat and humidity build, and the wet season arrives in earnest from December to March, when rain falls on about 16 days a month in Cairns.

On the outer reef off Cairns the water cools to about 25°C in July and August, warms to about 27°C in October and reaches about 29°C from January to March. The warm months are also stinger season: box jellyfish and Irukandji are most common in coastal waters from November to May, which is why the boats hand out full-body lycra suits in those months.

The reef’s wildlife has seasons of its own. Humpback whales migrate north along the reef from about May to September, dwarf minke whales gather on the Ribbon Reefs north of Port Douglas in June and July, and the corals spawn on a few nights after a full moon between October and December. Turtles, reef sharks, rays and the reef fish are there in every month.

Month by month

These are long-term averages, not a forecast: wind at Green Island, a reef island about 27 km off Cairns, air temperature and rain at Cairns Airport, and the water temperature recorded on Thetford Reef, an outer reef visited by Cairns day boats.

January to March is the wet season at its height. The water is at its warmest, the winds are light in January and February, and February and March are much quieter for travel to Cairns once the summer school holidays end in late January. On land it is hot and humid, with heavy rain on many days, and this is the heart of the cyclone season. Trips sail in showers, but storms can close the port or cancel a day, so a stay of a few nights gives you room to move your reef day.

April and May are a transition. The rain eases through April and the air dries out in May, but the trade winds are back, so the crossing can be bumpy. May is the last month of stinger season.

June to August is the dry season at its most settled on land, with cool nights, highs of about 26°C and rain on only five to seven days a month in Cairns. It is also one of the windiest stretches on the reef, with the coolest water of the year, at about 25°C, so a wetsuit helps on a long snorkel. It is humpback whale season, and the July school holidays make it a busy time to travel.

September and October keep the dry weather while the trade winds ease and the water warms. Rain falls on about five or six days a month in Cairns, the water reaches about 25°C in September and 27°C in October, and stinger season has not yet begun. The Queensland spring school holidays fall across late September and early October.

In November and December the winds are at their lightest and the water reaches 28 to 29°C; these are the first months of stinger season and the usual coral spawning window. The heat and humidity build, afternoon storms become more common, and the summer school holidays begin in mid-December.

Wind, waves and seasickness

Wind is the condition you notice most on a reef day. The outer reef off Cairns is 50 to 70 km out, and the crossing takes up to two hours each way on open water. On a breezy day the boat moves more, the water at the reef is choppier and it is harder to keep your mask clear, so wind changes how comfortable the whole day is.

On average the afternoon wind at Green Island is strongest in June, at about 38 km/h, and lightest in December, at about 23 km/h. Boats sail in a wide range of conditions and can switch to more sheltered moorings: Passions of Paradise, for example, picks its sites each day from reefs including Flynn, Hastings, Milln, Moore, Norman and Thetford to suit the weather. A calm day in July can still beat a windy one in October, which is why the forecast for your own date matters more than the monthly average once you are booked.

If you are prone to seasickness, take a remedy before you board rather than once you feel unwell, and stay out on deck in the fresh air.

Stinger season

Marine stingers, including box jellyfish and Irukandji, are present in tropical Queensland waters all year, but the Queensland Government says the risk is higher from November to May. Tourism Australia notes that the risk out on the reef is low, but stinger suits are still recommended, and the reef boats provide full-body lycra suits; Sunlover, for one, gives every guest a free suit all year. A suit also keeps off the sun, so you can wear one in any month.

The bigger change is on the mainland. From November to May, swim inside the stinger nets where they are provided, such as the enclosure at Four Mile Beach in Port Douglas; Douglas Shire Council notes that the nets give a high degree of protection against box jellyfish but are not completely stinger-proof. If someone is stung, call 000 and alert a lifeguard or the crew.

The wet season and cyclones

Cairns gets most of its rain from December to April, and February is usually the wettest month, with more than 400 mm on average. For a reef day the rain itself matters less than you might expect: you are wet in the water anyway, the boats have covered cabins, and the showers often pass. What can change a trip is a storm or a tropical cyclone; Sunlover and Quicksilver both describe weather cancellations as rare, and none of the five operators we checked publishes a rate. The cyclone season runs from 1 November to 30 April; most weeks bring no cyclone, but one nearby can close the port, cancel trips and disrupt flights for several days.

In the wet season, book your reef day early in your stay, avoid a non-refundable flight the evening after it, and watch the Bureau of Meteorology’s warnings in the days before you go.

Whales, coral spawning and other wildlife

Humpback whales migrate north along the Queensland coast from about May to September, and the Great Barrier Reef Marine Park Authority describes the Whitsundays as an important calving ground. They are sometimes seen from the reef boats and from scenic flights, and the Outer Edges scenic flight from Cairns lists July and August for spotting them, but no trip can promise a sighting.

Dwarf minke whales gather on the Ribbon Reefs, north of Port Douglas, in June and July. Swimming with them is allowed only on trips run by operators whose Marine Parks permit is endorsed for it, so check before you book if this is the reason for your trip.

The corals spawn one to six nights after a full moon between October and December; inshore reefs usually spawn after the October full moon and outer reefs after the November or December one. It happens after dark, so you see it on a night dive from an overnight boat, not on a day trip, and the exact night cannot be guaranteed.

Turtles, giant clams, reef sharks and the reef fish are there all year.

How busy the reef gets

Book further ahead for the Queensland school holidays, when families from across the state are free to travel: the summer holidays from mid-December to late January, two weeks around Easter, two weeks from late June to mid-July, and two weeks across late September and early October. Cairns Airport handles the most passengers from July to October, about 460,000 to 490,000 a month in 2025, against about 310,000 in February, the quietest month. That counts everyone flying in and out of the region, not people on the boats, but it shows when demand is highest.

Book popular boats, dive places and scenic flights as soon as your dates are fixed. February and March, outside the school holidays, are much quieter for travel to Cairns, although they are also among the wettest months.

Check your date

Pick a day to see whether it falls in stinger season, the cyclone season or a holiday, with the wind, wave and rain forecast for the outer reef off Cairns for the next week or two, and the usual conditions further ahead.

Which trip suits which season

In any month, a full day on the outer reef gives you the most time in the water. The Passions of Paradise premium catamaran, the most-reviewed reef day trip from Cairns, visits two outer reef sites and includes snorkelling gear, lunch and wetsuits or lycra suits depending on the season. Silverswift visits three sites among Flynn, Pellowe, Milln and Thetford reefs, which suits divers.

In the windier months from April to August, a pontoon gives you a stable platform at the reef and things to do out of the water. The Sunlover outer reef pontoon day adds a semi-submersible, a glass-bottom boat and an underwater observatory, which also suits non-swimmers. For the coral spawning or a minke season trip, look at overnight boats such as the two-day dive and snorkel trip from Cairns and check whether it includes a night dive.

To compare every option, see our guides to Great Barrier Reef tours from Cairns, Port Douglas reef tours, snorkelling tours from Cairns and scuba diving from Cairns.

Port Douglas and the Whitsundays

Port Douglas boats run to Agincourt Reef and the Ribbon Reefs, about an hour north of the Cairns sites, where the seasons follow the same pattern: the water on Agincourt Reef averages about 25°C in July and August and about 29°C from January to March.

The Whitsundays, about 500 km further south, are cooler in winter. The water around Hook Island averages about 22°C in July and August, so a wetsuit is more useful there, and Hamilton Island has rain on only about three days a month from August to October. Humpback whales come to the Whitsundays to calve from about May to September. See our Airlie Beach reef tours compared for the trips from there.

How we know

Frequently asked questions