What is the urban heat island effect?

The Urban Heat Island (UHI) has been observed in cities around the world where the urban area has higher temperature than surrounding rural and suburban areas¹

• Urban development replaces natural land surfaces and vegetation with building materials and hard paved surfaces that absorb solar radiation and heat during the day
• Waste heat from air conditioners used to cool buildings or heat generated from the engines of vehicles can also be trapped and absorbed in cities
• Accumulated heat from the city is slowly released at night which keeps temperatures higher than surrounding natural areas
• Fewer trees and plants in the urban landscape to provide shade and the cooling benefits of evapotranspiration that lower the local temperature
• Hard surfaces in cities means that there are less opportunities for rainfall to be retained in the landscape and infiltrate the soil which reduces the potential for evaporation which can contribute to cooling

Urban heat island effect in Darwin

Urban overheating can have serious consequences on thermal comfort, energy consumption, health and the economy². Research from the University of New South Wales found that the CBD is between 2–3 °C warmer than the surrounding suburbs³. CSIRO has CSIRO mapped land surface temperatures across Darwin during the dry season, which found that land uses associated with thermal hot spots included⁴:

• Areas with large numbers of buildings, roofs, paved surfaces and little vegetation cover
• New housing developments where trees and gardens are still establishing
• Areas with large patches of bare ground and dry grass (which are likely to be cooler during the wet season)