Over the next 40 years, the number of sweltering summer days in New York City could double or even triple, making it as hot in 2050 as Birmingham, Alabama, is now.
The sea level surrounding New York is also likely to rise by 2 feet (0.6 meter), jeopardizing lower-lying homes and businesses, according to a report commissioned by the city to be released on Tuesday.
It is the first time New York City has updated its projections about the impact of climate change since Superstorm Sandy struck seven months ago.
The storm - three times as massive as Hurricane Katrina in 2005 - killed more than 100 people in New York, New Jersey and Connecticut, knocked out power to millions and caused billions of dollars in damages.
The report also forecasts the number of days at or above 90 Fahrenheit (32 Celsius) will rise to as many as 57 in 2050, up from roughly 20 days a year now.
Some of the city's underground infrastructure could become too hot, "like being in an oven beneath the street," said Deputy Mayor for Operations Cas Holloway at a news conference on Monday. New York has a vast underground subway system, parts of which flooded during Sandy.
Mayor Michael Bloomberg is scheduled on Tuesday to propose how the city could prepare for the forecasted climate change - and how much such a massive undertaking could cost taxpayers.
Bloomberg, a political independent, said climate change may have been a factor in Superstorm Sandy. He endorsed President Barack Obama just after the storm because of Obama's stance on climate change.
New York City has already laid out plans to spend about $1.7 billion in federal disaster aid to recover from the storm. Even more is supposed to flow to the region under the $50 billion supplemental Sandy relief package Congress approved earlier this year.
Holloway declined to say how much the improvements and changes could cost or who would pay for it, deferring to Bloomberg's upcoming presentation.
But "there is going to be a real cost to inaction" if the city fails to deal with climate change, Holloway said.
(Reporting by Hilary Russ; Editing by Lisa Shumaker)