On 15 March 2018, a tropical low formed in the Arafura Sea north of the Northern Territory; the Bureau of Meteorology issued a cyclone watch for Darwin, the Tiwi Islands and parts of the north-west Top End.

Drifting east-south-east, north of the Tiwi Islands, the low developed into a Category 1 tropical cyclone early on 16 March and was named tropical cyclone Marcus. Marcus reached Category 2 status in the hours before it crossed the Northern Territory coastline on Saturday 17 March; it passed directly over Darwin just before midday, an hour earlier than originally estimated. Wind gusts of 130 kilometres per hour were recorded in Darwin, and a new March record of 126 kilometres per hour was recorded at Darwin Airport.

With winds easing, the city’s cyclone shelters closed by about 8.00pm and residents were sent home. That evening however, Northern Territory Emergency Service (NTES) staff worked through around 400 incidents across the region.

Marcus eased to a Category 1 cyclone; by the evening of the following day, heavy rain over the Top End started to abate.

However, as it passed over Western Australia’s northern Kimberley, Marcus again intensified to Category 2. People in or near coastal and island communities from Wyndham to Mitchell Plateau, Beagle Bay and Cockatoo Island were warned to prepare for the approaching storm.

Marcus intensified rapidly after it passed over the northern Kimberley and moved west into open waters, reaching Category 5 over the Indian Ocean on 21 March – the most intense tropical cyclone in the Australian region since severe tropical cyclone Monica in 2006. Marcus then weakened rapidly as it moved south and transitioned into an extratropical cyclone by 25 March.

Marcus was the strongest tropical cyclone to hit Darwin since severe tropical cyclone Tracy (Category 4) in December 1974. Marcus caused the cancellation of major events and all flights in and out of Darwin. Approximately 26,000 homes were affected by electricity outages due to destructive winds, in areas as far south as Batchelor and Adelaide River. Thousands of residents in the greater Darwin area were warned to boil water before drinking it. Thousands of trees were destroyed across Darwin, including many shallowrooted African mahoganies planted after Tracy.

Public schools and non-essential public service agencies were closed, some for several days, while clean-up efforts continued. Removing downed trees and power lines from roads was a priority. The city’s water supply was affected; residents were urged for nearly 48 hours to boil tap water before using it. The Health Department issued a warning for melioidosis, a life-threatening disease spread by contact with soil, mud and surface water.

The clean-up in Darwin was coordinated by the NTES and included more than 200 City of Darwin staff. Through Defence Assistance to Civil Community (DACC) arrangements, One Brigade Emergency Response Force assisted with tree clearance in public premises and an Australian Defence Force Joint Task Force assisted with general street clearance. The defence deployment included United States Marine Corps troops based in Darwin.

While there were over 6,400 insurance claims, and insurance costs topped A$75 million, Marcus caused no fatalities. And unlike Tracy, Marcus caused relatively little structural damage; in part due to less severe winds as well as improved building codes for cyclone conditions established after Tracy. The Insurance Council of Australia reported that most claims were for damage caused by falling trees.