Urbanisation is increasing rapidly, especially in the developing world, with many more people living in slums and informal settlements, Kyte told IPS from London.
As climate change disrupts rainfall patterns and generates more extreme weather in the coming decades, leading to poor crop yields, rural populations will flood cities. Escalating numbers of urban poor will suffer, with temperatures magnified by the "heat island effect" of the constructed urban environments.
Safe drinking water will also be harder to find, especially after floods, contributing to greater water-borne diseases such as cholera and diarrhoea.
Coastal regions like Bangladesh and India's two largest coastal cities, Kolkata and Mumbai, will face extreme river floods, more intense tropical cyclones, rising sea levels and very high temperatures.
"Huge numbers of urban poor will be exposed in many coastal cities," Kyte said.
"We face a huge challenge over the next 20 years to... redesign our cities to protect them from climate change," Kyte predicted, even as cities already face a huge infrastructure investment gap.
One trillion dollars a year needed to be invested every year by 2020 by some estimates, Kyte said, adding that "to build climate resilience into cities will take another 300 to 500 million dollars a year".