The Top End is a tropical region where the seasons of temperate climate - spring, summer, autumn and winter - have no relevance. Most rain falls from December-March with thunderstorms between October-November, and in April. Annual rainfall varies from 800 mm in southern Top End to 2000 min on the Tiwi Islands.

Two major climatic features dominate. Monsoon systems arrive about late December providing humid, wet conditions till about April. Then from May to September high pressure systems travel east across southern Australia sending dry, cool winds across the Territory. The former season is called the Wet and begins officially on Ist October. The latter is the Dry and its official starting date is Ist May. The hot and humid time before the rains is known locally as 'the build-up', and the strong winds that occur about April are called the 'knock-em-downs' (they flatten the tall grass). Cyclones' occur from November to May with most occurring in March.

Maximum daytime temperatures range from 28-35'C near the coast at the hottest time of the year, and are up to 1WC cooler in the Dry Season. Inland temperatures are more extreme. Humidity also fluctuates widely, from 90% in the Wet Season to less than half that in the dry. Inland is less humid.

Climate change in NW Australia

Rainfall and the number of rainy days have increased in northwest Australia since the early 1900S,2the most notable change occurring in the late wet/early Dry Season. Some bird species may have been affected, for instance those that nest at that time of year, and birds which move away from the coast during the Wet Season.

Kunwinjku Seasons

The traditional people of Arnhem Land follow a different system of climate recognition, dividing the year into six seasons which begin and end according to weather and behaviour of key animals and 'calendar' plants.

Gudjewg (January-March) features monsoonal downpour, floods and occasional cyclones. At night roads are frequented by frogs hunting insects and birds hunting both. Other birds disperse and many move inland.

Banggereng (March-June) is hot and humid. The last storms occur accompanied by 'knock-em-down' winds. Waterfowl vanish from waterholes to breed. Migratory birds arrive in the Top End on their return to breeding grounds in Siberia and elsewhere. Many areas are inaccessible because of flooding. When manbadje (speargrass) drops its seed people know that goose eggs are ready to collect.

May-June, the beginning of the dry, cool time is Yegge, and July-August, the end Wurrgeng. From June on these seasons are relatively boring on the birding front as few species are breeding! However many eucalypts, grevilleas and acacias are blooming, and nectar-feeders and gleaners are busy. Toward the end few trees are flowering and many are dropping leaves.

The 'build-up' (September-December) is Gurrung (which also means 'little mother'), and is a very hot, steamy time. Old-timers also refer to it as the 'suicide season'3 but birdwatchers should not be put off - this is the best time for birdwatching in the Top End as birds gather around shrinking waterholes or ready themselves to breed.

Gunumeleng, the time of storms, follows (November-December/January). To long-time locals this is the best time of the year with magnificent thunderstorms and beautiful sunsets. Many native trees are now fruiting and birds are breeding. This is also the time of tropical cyclones, also known as hurricanes or typhoons, area notorious feature of the Top End climate. The best known, Cyclone Tracy, flattened Darwin on the night of 24 December, 1974, killing some seventy people, injuring many more and devastating the city. It also wrecked surrounding mangroves and bushland, which took years to recover. Although such events are exceptional, electrical storms and blustery weather are normal features of the wet season.