Philadelphia could be in for up to 15 times the annual number of days above 95 degrees by century's end.
That's according to a city climate change report released this month, which projects the number of 95-degree-plus days to climb from a recent average of three a year to between 15 and 44 by the year 2100.
The report projects milder winters, with the number of days below freezing anticipated to fall from the recent average of 93 a year to between 33 and 60 by century's end.
Hotter summers may lead to more heat-related deaths, the reports said, but milder winters may prevent some cold-weather deaths.
The hotter, wetter weather described in the report is in line with previous regional projections, but experts say the report offers new details on local precipitation patterns.
"We anticipate that there will be more precipitation, it'll be about 6 inches over the year," said Sarah Wu, policy and outreach manager for the Mayor's Office of Sustainability, which commissioned the report.
"That would be fine if it was all going to fall Seattle-style, in light drizzle over the course of the year relatively evenly," Wu said.
"But the projections show that we're actually going to probably get most of that additional precipitation in bigger storms, so a lot of rain coming in a short period of time, which is a much different ball game for our systems to handle."
Increased heavy precipitation will likely increase runoff, potentially flood roads, and speed erosion of bridge foundation supports, the report said.
About 2 inches of the annual liquid precipitation increase by 2100 is projected to fall during winter, though it is unclear what form (rain, sleet or snow) that precipitation would take.
The Mayor's Office of Sustainability has been sharing the data with city agencies to help them prepare for future weather changes.
"We were quite shocked to see the projections," Streets Commissioner David Perri said.
"An additional 1 inch of winter precipitation typically would result in about an additional 1 foot of snow in the city of Philadelphia area," Perri said, putting more of a burden on the city's snow-removal systems.
Perri said the data is pushing the department to increase brining operations.
The city now sprays about 30 miles of city streets with a saltwater mixture before storms to prevent snow and ice from sticking.
Officials plan to expand that to several hundred miles over the next five to seven years.
The city plans to use the report to begin to develop a climate change adaptation plan, to be released this summer.