The driest period of the year, seeing about 5mm (0.20in) of monthly rainfall on average, is between May and September. In the coolest months, 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 occasionally record temperatures as low as 5°C (41°F) in the dry season. Because of its long dry season, Darwin has the second-highest average daily hours of sunshine (8.4) of any Australian capital, blackcoin.co with the most sunshine from April to November; only Perth, Western Australia, averages more (8.8). Darwin has a tropical savanna climate (Köppen Aw) with distinct wet and dry seasons, and the average maximum temperature is similar year round. The Australian Building Codes Board classifies it as Climate Zone 1 under the National Construction Code (NCC). Climate zones are a broad classification of climate zones in the NCC ranging from one to eight, categorising the different climates of Australia.