Stretching more than 2300 km (1300 miles) from Bundaberg, just north of Brisbane and well beyond Australia’s northernmost point towards Papua New Guinea, the Great Barrier Reef is a breathtakingly vast natural wonder.
Supporting a unique and diverse ecosystem both above and below the water, the reef is home to thousands of species of wildlife and marine life and is a destination that is favoured by tourists and scientists alike.
Yet despite its seemingly fragile beauty and tropical tranquillity, weather in the Great Barrier Reef can be anything but. Heavily impacted by seasonal weather patterns, enjoyment of the reef, alongside effective reef management and conservation efforts, must be carefully planned.
So what is the weather like in the Great Barrier Reef? Let’s take a closer look.
General Climate Patterns
When it comes to weather in the Great Barrier Reef, Australia, there are two distinct seasons. These are Winter (dry season) between May to October and Summer (wet season) which occurs during November to April.
Overview Of The Region’s Climate Zones
While the Great Barrier Reef is broadly referred to as having a tropical climate, it falls into two distinctly tropical and sub-tropical climate zones recognised in Australia.
From its Northernmost point down to just below Proserpine, the reef is in climate zone one, which as a tropical zone features high-humidity summers and warm winters.
From Bundaberg at its Southern end to just north of Mackay, the reef is classed as being in climate zone two which is subtropical and has warm humid summers and mild winters.
Influence Of Ocean Currents & Atmospheric Conditions
Great Barrier Reef weather conditions are strongly influenced by both ocean currents and atmospheric activity.
For example, the East Australian Current (EAC), carries warm water from the northern tip of Australia along the eastern coast and down past Tasmania in the south. Warm sea surface temperatures driven by the EAC can enhance convection, increasing cloud formation and rainfall. This interplays with the equatorial low-pressure zone that dominates in the summer months and also causes frequent rain and thunderstorms.
During the winter months, a sub-tropical high-pressure zone prevails for a clearer weather forecast. This also sees strong north-westerly trade winds that tend to slow the southward-moving EAC down, cooling the ocean, reducing convection and further supporting dry, sunny weather.
Wet Season
Characteristics Of The Wet Season In The Great Barrier Reef
The wet season is driven by the monsoon trough and the Intertropical Convergence Zone (ITCZ), which brings moist air from the equator, leading to frequent thunderstorms and heavy downpours.
Alongside increased rainfall, high humidity, and warmer sea temperatures are also present during this season. Daily outside temperatures peak at around 31 degrees with lows of around 22 degrees, ocean temperatures can be as high as 30 degrees.
Rainfall Patterns, Humidity Levels & Storm Frequency
Humidity at the reef during the wet season is between 67-78%, it does not usually rain all day during this period, instead tropical downpours can be expected in the afternoons and evenings.
On occasion, loud and visually dramatic thunderstorms/electrical storms can also be experienced.
Dry Season
Features Of The Dry Season At The Reef
The dry season is marked by lower humidity, cooler temperatures, less rainfall, and refreshing breezes. While ocean temperatures are also cooler than during the wet season, they remain a comfortable 24 degrees on average.
Temperature Variations, Wind Patterns & Sea Conditions
A maximum daily temperature of around 29 degrees and lows of 25 degrees are typical of this season. The southeast trade winds, while breezy onshore, may be a little stronger at times when heading further away from the coastline into the reef.
With minimal rain and clear skies, the ocean is typically quite calm and visibility for snorkelling and scuba diving is at its best.
Cyclone Season
Overview Of Cyclone Season In The Great Barrier Reef
Tropical cyclones are significant weather events that impact the reef, typically occurring during the wet season. So much so that locally, cyclone season and wet season are often used interchangeably to collectively describe the months of November through to January.
According to data collected by the Bureau of Meteorology, on average, there are around four tropical cyclones that affect the Great Barrier Reef in each cyclone season. They spawn in this region due to the interaction of warm air over warm seawater, which gives added strength to summer storms.
Impact Of Cyclones On Reef Health & Ecosystem Dynamics
Cyclones can cause strong winds, heavy rainfall, storm surges and very large, powerful waves which may lead to significant physical damage to coral structures. They may also contribute to increased sedimentation and freshwater influx to the reef which causes further stress to the marine ecosystem.
While the reef is capable of recovering, it can take decades to properly do so and this is hampered when there are multiple cyclones in quick succession. When a reef is completely reduced to rubble, it becomes destabilised and new coral growth is more susceptible to damage in future. This can also see vital marine habitats destroyed and the death of many species that reside there.
Seasonal Changes in Marine Life
A multitude of marine species with complex migration patterns and breeding behaviours reside in or interact with the Great Barrier Reef during different seasons.
Migration Patterns & Breeding Behaviours Of Marine Species
Key marine species in the Great Barrier Reef that engage in seasonal migration and breeding activities include:
Coral Trout
Great Barrier Reef coral trout exhibit seasonal migration patterns primarily driven by spawning cycles. They tend to move from their home reefs to specific spawning aggregation sites between the cooler months of September to December.
These migrations can cover distances of up to several kilometres, often timed with lunar cycles, particularly around the full moon, which triggers spawning events.
Green Sea Turtles
An endangered species, green sea turtles undertake extensive migrations between their feeding grounds and nesting beaches. These migrations can span thousands of kilometres across the Pacific Ocean.
Female green turtles that hatched on the Great Barrier Reef, return to these same beaches (natal homing) to lay their eggs. Migration and nesting season typically occurs from November to March during the wet season when the water is warmest.
Humpback Whales
Humpback whales migrate annually from their feeding grounds in the cold waters of Antarctica to the warm waters of the Great Barrier Reef for breeding and calving. The migration covers approximately 5,000 to 6,000 kilometres, with the whales arriving in the reef region between June and October.
During their time at the reef, the whales will engage in mating activity or calve their young. Humpback whales give birth in the warm, sheltered waters of the reef with the mothers and calves remaining in the area for several months before returning to Antarctic feeding grounds.
Influence Of Seasonal Weather Patterns On Coral Spawning & Growth
Also a marine animal, corals in the Great Barrier Reef engage in synchronous mass spawning events, typically occurring once a year after the full moon at the close of the dry season in October or November.
During these events, corals release millions of eggs and sperm into the water column simultaneously, ensuring cross-fertilization.
Human Activities and Seasonal Tourism
Tourist Activities & Visitation Trends Throughout The Year
Around 2.19 million people are estimated to visit the Great Barrier Reef each year. This number comprises domestic and international travellers with the most popular spots to visit being Cairns, Port Douglas and the Whitsunday Islands.
The dry season is considered the best time to visit the reef due to enhanced underwater visibility, more comfortable temperatures and fewer incidences of ‘stingers’ or jellyfish which proliferate in the summer.
Regardless of season, tourists consistently engage in reef-related activities throughout the year. From snorkelling to scuba diving, wildlife and marine life tours, whale watching, research station visits and more, there is a huge variety of tourist activities to enjoy year-round.
Management Strategies For Sustainable Tourism During Different Seasons
Throughout the year tour operators are incorporating conservation and sustainability messages into their tours and offering opportunities for tourists to participate in reef conservation activities, such as coral planting and beach cleanups.
Additionally, to accommodate migration and breeding activities, seasonal closures do apply to some islands and some activities are restricted or not allowed. Visitor numbers to some areas of the reef may also be capped or limited due to regeneration or research projects being undertaken during the dry season.
Climate Change & Seasonal Variability
Effects Of Climate Change On Seasonal Weather Patterns
Climate change is increasing the frequency and intensity of severe weather events in the Great Barrier Reef. By causing increased ocean temperatures and higher rainfall, the reef and nearby coastal areas are subject to more cyclones, flooding and storms during the wet season than ever before.
Potential Implications For The Great Barrier Reef Ecosystem
Marine heatwaves linked to climate change have already caused multiple mass coral bleaching events on the Great Barrier Reef between 1998 and 2024. This is estimated to have reduced shallow-water coral reefs by as much as 50%.
This paired with sediment dumping and high-strength waves during cyclones is making it incredibly challenging for the reef ecosystem to recover. Making conservation efforts and research into mitigating the effects of climate change crucial.
