Two weeks before Christmas 1974, a cyclone called Selma had threatened Darwin, then veered away and came to nothing. When warnings began circulating about a second system on Christmas Eve, a lot of Darwin residents reasonably assumed it would do the same. It didn't.
A quiet build-up
Cyclone Tracy first formed as a tropical low over the Arafura Sea, northeast of Darwin, on 20 December 1974, and had strengthened into a full tropical cyclone by the following day. Through Christmas Eve, Darwin's Bureau of Meteorology issued cyclone warnings as the system tracked closer, but the timing worked against them. It was Christmas Eve. Rain had been falling since around lunchtime and the wind had been building through the afternoon, but radio warnings about an approaching cyclone competed with the sound of presents being wrapped and Christmas dinners being prepared. Combined with the recent false alarm from Cyclone Selma, most residents didn't evacuate or seriously prepare. Many went ahead with Christmas parties as the wind and rain outside continued to build.
The strike
Tracy crossed the coast near Fannie Bay at around 3:30am on Christmas morning, and the most severe damage began after about 10pm the previous night as the cyclone closed in. It was, by world standards, a physically small storm, with gale-force winds extending only around 40 kilometres from its centre, but what it lacked in size it made up for in concentrated intensity directly over a populated city. Wind gusts were recorded at 217 km/h at Darwin Airport before the anemometer's needle was bent in half and the instrument failed entirely; some later estimates suggest the true peak may have reached as high as 280 km/h. As the eye passed directly over the city between roughly midnight and 7am, torrential rain fell throughout, including 255mm in a single 12-hour window overnight, with two separate 30-minute bursts on either side of the eye each dumping around 145mm on their own.
Because the eye crossed in the dead of night, most residents were already indoors when the worst of it hit, and the fact that it struck under cover of darkness is part of why the death toll wasn't far higher. Most of the 66 confirmed deaths, 53 on land and 13 lost at sea, were caused by flying debris or by houses collapsing on the people sheltering inside them.
The scale of the damage
By dawn, approximately 70% of Darwin's buildings had been destroyed or left severely damaged, and around 10,000 of the city's homes were gone. Every public utility failed simultaneously: no electricity, no running water, no sewerage, no phone lines. For a tropical city at the height of the wet season, the combination of destroyed sanitation and standing water created a serious risk of disease outbreak almost immediately, which is what drove what happened next.
The evacuation
Within days, Darwin saw the largest evacuation and reconstruction operation in Australia's peacetime history. Of the roughly 47,000 people in Darwin that Christmas, over 35,000 were evacuated within a week, the great majority by military and civilian aircraft in one of the largest airlifts in Australian history, with others driving out along the Stuart Highway. By New Year's Day, the city's population had fallen to around 11,000, mostly those who stayed to help with the clean-up. Word of the disaster spread quickly through the rest of the country: within 24 hours, the population of Alice Springs alone had raised more than 00,000, a substantial sum at the time, to help Darwin's evacuees.
Rebuilding
In February 1975, the federal government established the Darwin Reconstruction Commission, tasked with rebuilding the city within five years. The Commission oversaw the reconstruction of housing and key infrastructure through to 1978, by which point Darwin's population had already recovered to roughly the level it had been at before the cyclone struck. One of Tracy's lasting legacies was far stricter building codes introduced across northern Australia afterward, specifically aimed at making sure future homes could withstand cyclone-force winds, a direct response to how completely so much of Darwin's housing stock had failed that Christmas morning.