The number of nights with extreme heat in Hong Kong will surge in the coming decades and the city will see even heavier rainfall, according to researchers who are urging the authorities to step up disaster mitigation plans.

A collaborative study between Chinese University, the University of Hong Kong and the University of Science and Technology has found that the number of hot nights in the city will increase by 50 percent by the 2040s.

They also predict that hourly rainfall could hit 230 millimetres on occasion, which would be 40 percent higher than the record set this year.

The researchers on Monday warned that the government's current plans for dealing with extreme weather situations might not be sufficient in the future.

"If the problem comes very often, then you have to have a proactive way to deal with the problem. You should try to predict and deal with it before it happens to minimise the impact," said project leader Professor Edward Ng.

"There are a number of policies and protocol changes that you may need to adjust in order to cope with this kind of more frequent event that is going to come."

The researchers said the authorities should review and update classifications of extreme weather regularly, and develop emergency response protocols, such as flood prevention measures in high-risk areas.

They also warned that high-intensity developments could increase the "urban heat island" effect in the city, and urged officials to consider this when it comes to urban planning.