Dive Seasons In Cairns | Month By Month Guide
What is the best time of year to dive the Great Barrier Reef off Cairns? There is no definite answer to this question. Cairns is a tropical port city, offering scuba divers the closest mainland access to the Great Barrier Reef, which means less time travelling and more time diving! Bordered by towering rainforest mountains on one side and the Coral Sea on the other, Cairns has two distinct seasons ‘wet’ (summer and autumn) and ‘dry’ (winter and spring).
The ‘wet’ season is self-explanatory. This is the time of year Cairns receives most of its annual rainfall and has quite high day time temperatures and humidity. For visitors, the ‘wet’ season (December – May) is generally considered the low season (which means there are more likely to be some great diving specials available!).
The ‘dry’ season (June – November) has lower day time temperatures, humidity and generally, much less rainfall: this is the high season, so there are more visitors and less availability on the dive boats (best to book ahead at this time of year!).
weather averages for cairns
|Max ° C||Min||Rainfall mm||Water Temp|
As to the best time of year to visit and dive, anytime is a good time to dive on the Great Barrier Reef off Cairns! Some of our best diving has been experienced during the ‘wet’ season (thanks to warm waters), while the ‘dry’ season offers visitors more comfortable day time temperatures and conditions, and once in a lifetime opportunities to swim and dive with Dwarf Minke Whales (more on this below). For your information and reference, we have prepared a month by month overview of Cairns diving conditions and what you can expect to see (see below).
Cairns’ Great Barrier Reef water temperature varies throughout the year, from a comfortable 29 degrees in summer (December – February) to 22 degrees in winter (June – August). While wind and visibility fluctuates daily, pending season and prevailing weather conditions, the marine life on the Great Barrier Reef does not, offering memorable diving all year round.
Indeed, it is the Great Barrier Reef’s biodiversity that make it one of the seven wonders of the natural world. Home to more than 1,500 fish species, 411 types of hard coral, one-third of the world’s soft corals, 134 species of sharks and rays, six of the world’s seven species of marine turtles and more than 30 species of marine mammals, it is always teeming with life. In addition to the ‘usual’ suspects (fish of all shapes, colours and sizes, reef sharks, rays, moray eels and turtles) there are some ‘seasonal’ creatures and events that come and go on Cairns Great Barrier Reef, including the annual appearance of Dwarf Minke and Humpback Whales, coral spawning and the turtle breeding season. These are outlined in the below copy, in the ‘what can I expect to see’ text.
January is a great month to go diving off Cairns. This is a summer month and the water temperature can be expected to be a balmy 29 degrees Celsius (84 Degrees Fahrenheit). There is no need for wet suits. Lycra suits are provided on all dive boats, providing protection from the sun and jellyfish. Being close to the equator, Cairns does experience monsoonal weather patterns. In January the days are hot and rainfall is common (but you get wet diving anyway). Tropical cyclones can occur in January and dive operators choose their locations to suit the conditions.
What can I expect to see in January?
This month jellyfish, salps and siphonophores of every shape and complexity can be found in the water and are a favourite food source for fish and turtles. Some fish will start spawning in January, including damsels, wrasse, surgeons and parrotfish.
February is the last month of summer and traditionally a very ‘wet’ month in Cairns, with high rainfall. Cairns’ Outer Great Barrier Reef dive sites are all about 60km offshore, which means high coastal rainfall does not really affect diving conditions, unless there has been a high intensity cyclone, which is an infrequent occurrence. This is a great month to visit the tropical north, with warm waters for diving and the rainforest alive with flowing waterfalls and streams.
What can I expect to see in February?
This is also the time of year that many turtle species are nesting and hatching. The turtle activity attracts sharks and some of Cairns’ liveaboard dive operators offer extended trips to the remote northern reefs and islands, including Raine Island, allowing divers to witness this marine activity in the remote wilderness.
March is an exciting month for diving off Cairns, it’s the first month of autumn so the waters are still warm (around 28 degrees Celsius) and there is generally less rainfall around.
What can I expect to see in March?
Many juvenile fish are starting to appear on the Great Barrier Reef: look out for the juvenile Harlequin Sweetlips, which can be seen mimicking the movement of a poisonous flat worm. Also, Black-tipped Reef Sharks give birth this month with females having between 1 to 10 pups in the inshore estuarine nursery grounds, where the young remain for the next few years.
In April the water is starting to cool a little (we’re still a long way from needing wet suits) and the ambient daytime temperatures are starting to become a little cooler. The clear, blue waters are teeming with marine life and it’s a great time of year to go diving.
What can I expect to see in April?
Look out for the smaller marine life, such as nudibranchs, cowrie shells and pipe fish. Heads up, not all nudibranchs are nudibranchs: juvenile sea cucumbers mimic the poisonous colours of nudibranchs to fool their predators, so look closely to see if they have feet. This month many of the coral bommies will become hidden by glassies (clear coloured juvenile fish) and if you look closely, you can see the juvenile anemone fish playing hide and seek amongst the anemones.
May sees the water starting to cool down and some divers (especially those used to tropical diving conditions) may be taking advantage of the wet suits this month. This is a transitional time of year for weather in Cairns and with winter just around the corner, the trade winds start coming up from the south, triggering a change in population of many migratory species.
What can I expect to see in May?
As you explore swim throughs on some of the Outer Reef sites, look for gorgonian fans, Lion Fish and the 2-metre Queensland Grouper that frequents the reefs from Cairns.
The first month of winter! Water temperatures on Cairns’ Great Barrier Reef are usually around 23 degrees Celsius this month and wet suits are provided on all dive boats. This is an exciting month for diving as not only will you see the ‘usual’ wonders of the Great Barrier Reef, but you might also have an encounter with a Dwarf Minke Whale.
What can I expect to see in June?
Your first dive in June has the possibility of becoming a snorkel if the vessel is surrounded by the beautiful Dwarf Minke Whales. This is the only place on earth where you can swim and snorkel with these magical creatures. June is the start of Dwarf Minke Whale season that runs through until the end of July.
In July the waters of the Great Barrier Reef are a deep, clear blue: the sky is the only thing matching them for colour intensity. The mornings are crisp and cool and the water temperature on the Coral Sea reaches a low of 22 degrees Celsius (71 degrees Fahrenheit). There is very little rainfall this month and visibility is usually excellent. Note: It can be windy at this time of year and if you suffer from motion sickness, then we highly recommend taking some preventative medication on the morning of travel.
What can I expect to see in July?
This month Manta Rays can be seen in clearer waters of the Coral Sea.
Diving in August can see travel time to and/or from Cairns to the Great Barrier Reef ‘delayed’ by the presence of Humpback Whales. These magnificent mammals will often stop boats as they breach and tail slap the water nearby. It’s the last official month of winter and the water is as cold as it will get off Cairns (22 degrees Celsius - 71 degrees Fahrenheit). Note: It can be windy at this time of year and if you suffer from motion sickness, then we highly recommend taking some preventative medication on the morning of travel.
What can I expect to see in August?
August sees Humpback Whales visiting the Outer Reefs from Cairns until late in September, when they slowly return south with their calves. Migaloo, the world’s only all white Humpback Whale is a regular visitor to Cairns’ Great Barrier Reef at this time.
September is another great month to go diving from Cairns. The trade winds have started to drop down and often you will have days with total ‘glass out’ conditions. Visibility is usually excellent on Cairns’ Outer Great Barrier Reef dive sites and further north at Osprey Reef in the Coral Sea. Osprey Reef offers 1,000 feet drop offs and hundreds of reef sharks: this can only be visited on a liveaboard dive trip from Cairns.
What can I expect to see in September?
Some Great Barrier Reef fish species, including Snappers and Red Throat Emperors, start to aggregate in the reef’s shallows in preparation for spawning. You will also see many marine turtles feeding on sea grasses and algae.
We are well into spring now and the waters are warming back up. The winds have generally dropped off and diving conditions from Cairns on the Great Barrier Reef are looking good.
What can I expect to see in October?
This is the time of year that breeding activity begins for most seabird species, so if you happen to be going to an island or cay (Michaelmas Cay is a great place to visit right now) you may be able to experience the noise and activity associated with breeding season. This is also the time for turtle mating and nesting, so you may see more turtles around than usual.
Cairns is heating up this month and so is the Great Barrier Reef, in preparation for its annual coral spawning! In November you can ditch the wet suits and return to the lycra suits, with water temperatures returning to around 27-8 degrees Celsius. The winds are down and the pool is open, another great month for diving on Cairns’ Great Barrier Reef.
What can I expect to see in November?
If you are lucky enough to be here in Cairns diving in November for coral spawning, you will see the reef come alive with Decorator Crabs, Slipper Lobsters and Palao Worms. NB: coral spawning can occur in either November or December: for more information, please visit our coral spawning page.
Summer is here! Cairns offers hot, humid days and nights with the clear, blue waters of the Great Barrier Reef a cool retreat for divers. Underneath the surface, visibility is good and there is lots of life, following the recent coral spawning of the Great Barrier Reef.
What can I expect to see in December?
Lots of Great Barrier Reef fish breed in December. Keep an eye out for anemone fish (Nemo!), with their bright orange eggs, and Triggerfish. In particular be aware of (and careful of) the larger Titan Triggerfish. Summer is their breeding season and the time of year when these fish become quite aggressive. Divers will be provided with information and advice on this, onboard the dive boats.
Cairns Dive Seasons FAQ
When can I see whales / dolphins on the Great Barrier Reef?
If you are hoping to see whales on Cairns’ Great Barrier Reef then June / July is the Dwarf Minke Whale season and they are commonly sighted on the remote reefs of the Far Northern Ribbon Reefs. This is a popular time of year to visit, as these magnificent mammals are very inquisitive and commonly approach snorkellers and divers in the water. Humpback Whales are shyer and do not normally approach divers or snorkellers in water, however, it is quite common for them to offer displays of breaching, rolling and fin slaps, to passengers travelling to the Outer Reefs on day trips from Cairns, in late August to September. Dolphins can be seen all year round, most often seen playing in the bow water of a moving vessel. Occasionally divers in water may hear them calling with high pitched whistles and clicking, but it is extremely rare for them to approach Cairns divers.
Can I dive when it is raining in Cairns?
Yes, you can dive when it’s raining in Cairns, you are going to get wet anyway! Cairns has a tropical climate with an annual monsoonal ‘wet’ season. The weather is hard to predict and sometimes when it’s raining in Cairns, it’s not raining at the reef and vica versa. Rain itself will not impact on your day and diving.
Cyclones and diving on the reef, what’s the impact?
The Great Barrier Reef has evolved with tropical cyclones over thousands of years. A tropical cyclone is a severe weather system with high winds and rainfall. Its severity varies. Tropical cyclones can impact much of Queensland’s coastline, but are mostly experienced in the north, anywhere from Cape York Peninsula down to Mackay, during the summer months (December – February). Their impact on the reef varies, pending their intensity. There may be some coral damage, although the marine life is still present and can be seen by divers. As it is a natural process, the reef does recover from the impact of cyclonic events. Cyclones are closely monitored by dive operators, who adjust their operations to suit conditions. Generally, cyclones will only impact dive operations for a few days each year during summer. Of course the weather is variable and can not be predicted: for more information at the time of your visit, please contact Cairns Dive Adventures.
When is the best time of year to dive in Cairns?
Diving the Great Barrier Reef from Cairns can be brilliant at any time of year. For detailed information, please see our Dive Seasons In Cairns page.
Is it safe to scuba dive with jellyfish?
There are poisonous jellyfish (marine stingers) present in the waters around Cairns and the Great Barrier Reef at various times during the year. By taking appropriate precautions (wearing the lycra suits provided or for hire etc) and following the advice provided on the dive boats, scuba diving should be safe at any time. For more information on this, please see our Cairns Jellyfish Page.
Of course this is a guide only. Diving all year round on Cairns’ Great Barrier Reef you can expect to see turtles, sharks, bright corals, sting rays, pipefish, sea snakes, Queensland grouper, Maori wrasse and much more. For those interested in the smaller, colourful colours of nudibranchs, they can be sighted all year round as well.
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