Darwin has a tropical savanna climate with distinct wet and dry seasons and the average maximum temperature is similar all year round. The dry season runs from about May to September, during which nearly every day is sunny, and afternoon relative humidity averages around 30%.
The driest period of the year, seeing only approximately 5 mm (0.20 in) of monthly rainfall on average, is between May and September. In the coolest months of June and July, the daily minimum temperature may dip as low as 14 °C (57 °F), but very rarely lower, and a temperature lower than 10 °C (50 °F) has never been recorded in the city centre. Outer suburbs away from the coast, however, can occasionally record temperatures as low as 5 °C (41 °F) in the dry season. For a 147‑day period during the 2012 dry season, from 5 May to 29 September, Darwin recorded no precipitation whatsoever. Prolonged periods of no precipitation are common in the dry season in Northern Australia (particularly in the Northern Territory and northern regions of Western Australia), although a no-rainfall event of this extent is rare. The 3pm dewpoint average in the wet season is at around 24.0 °C (75.2 °F).
Extreme temperatures at the Darwin Post Office Station have ranged from 40.4 °C (104.7 °F) on 17 October 1892 to 13.4 °C (56.1 °F) on 25 June 1891; while extreme temperatures at the Darwin Airport station (which is further from the coast and routinely records cooler temperatures than the post office station, which is in Darwin’s CBD) have ranged from 38.9 °C (102.0 °F) on 18 October 1982 to 10.4 °C (50.7 °F) on 29 July 1942. The highest minimum temperature on record is 30.7 °C (87.3 °F) on 18 January 1928 for the post office station and 29.7 °C (85.5 °F) on both 25 November 1987 and 17 December 2014 for the airport station, while the lowest maximum temperature on record is 18.4 °C (65.1 °F) on 3 June 1904 for the post office station and 21.1 °C (70.0 °F) on 14 July 1968 for the airport station.
The wet season is associated with tropical cyclones and monsoon rains. The majority of rainfall occurs between December and March (the southern hemisphere summer), when thunderstorms are common and afternoon relative humidity averages over 70 percent during the wettest months. It does not rain every day during the wet season, but most days have plentiful cloud cover; January averages under 6 hours of bright sunshine daily. Darwin’s highest Bureau of Meteorology verified daily rainfall total is 367.6 millimetres (14.47 in), which fell when Cyclone Carlos bore down on the Darwin area on 16 February 2011. February 2011 was also Darwin’s wettest month ever recorded, with 1,110.2 millimetres (43.71 in) recorded for the month at the airport.
The hottest months are October and November, just before the onset of the main rain season. The heat index sometimes rises above 45 °C (113 °F), while the actual temperature is usually below 35 °C (95 °F), because of humidity levels that most would find uncomfortable. Because of its long dry season, Darwin has the second-highest average daily hours of sunshine (8.4) of any Australian capital, with the most sunshine from April to November; only Perth, Western Australia, averages more (8.8). The sun passes directly overhead in mid-October and mid-February.
The average temperature of the sea ranges from 25.8 °C (78.4 °F) in July to 31.5 °C (88.7 °F) in December.
Darwin occupies one of the most lightning-prone areas in Australia. On 31 January 2002 an early-morning squall line produced over 5,000 cloud-to-ground lightning strikes within a 60-kilometre (37 mi) radius of Darwin alone—about three times the amount of lightning that Perth, Western Australia, experiences on average in an entire year.