Today, the Earth is warming at an accelerated rate due to human activities. The primary driver of this trend is the burning of fossil fuels, such as gas, oil, and coal, to power transportation, buildings, and industry. Burning fossil fuels release greenhouse gases, which trap heat in the atmosphere. This acts like an insulating blanket around the planet.

This process, known as the greenhouse effect, is changing our climate. It is leading to more extreme weather events and affecting how we live, move, and care for one another.

What this means for Philadelphia

Philadelphia is experiencing more extreme heat and heatwaves because of climate change. Since 1970, average annual temperatures in the city have increased by nearly 4°F. Seven of the 10 hottest years on record have occurred since 2000, and nine of the 10 have occurred since 1990.

Heatwaves are periods of unusual hot and humid weather lasting multiple days. In Philadelphia, heatwaves are projected to become more common, last longer, and feel more intense.

By 2080, Philadelphia may experience the following extreme heat conditions (compared to a baseline period from 1985-2014):

• Average temperatures are expected to increase by approximately 5-8°F.
• The hottest day of the year could increase nearly 10°F, reaching 107°F.
• The number of days each year with temperatures reaching over 100°F could increase from less than one to nearly three weeks.
• Estimates call for up to five heatwaves per year, using Philadelphia’s heat health emergency thresholds.

Extreme heat is Philadelphia’s deadliest natural hazard to date. It can:

• Cause dehydration, heatstroke, and other harms to people’s health
• Worsen existing health conditions, like cardiovascular and respiratory diseases.
• Put certain vulnerable populations at greater risk of health harms. This includes outdoor workers, unhoused communities, pregnant people, the elderly, and young people.

The effects of extreme heat are not felt equally across Philadelphia. During the summer months, some neighborhoods can be nearly 30°F hotter on average than others. One key reason is the urban heat island effect. Cities and neighborhoods with fewer trees and green spaces tend to be hotter than surrounding areas because buildings, roads, and other hard surfaces absorb and retain heat. This is similar to the way a cast-iron pan will radiate heat once its temperature increases and remains hot long after the burner is turned off.

Historically, underserved and under-resourced neighborhoods and communities of color are more likely to be harmed by extreme heat. Residents in these communities experience:

• Higher rates of health conditions that can increase the risk of heat-related illnesses. This includes asthma, heart disease, and diabetes.
• The highest energy burden (proportion of income spent on energy bills).
• Less access to reliable and efficient cooling systems like mini-splits AC, heat pumps, and newer air-conditioning units.
• Older housing that is drafty and harder to cool.

This pattern of unequal exposure and vulnerability shows that climate change is not only a public health issue; it is also a racial and social equity issue.

Philadelphia is working to address climate change. The City has programs and strategies designed to reduce citywide carbon emissions, while preparing Philadelphia for the impacts of climate change. The goal is to go carbon neutral by 2050. The programs and strategies are:

• TreePhilly, an urban forestry program of Philadelphia Parks & Recreation and Fairmount Park Conservancy. Trees and greenspace absorb carbon, the main greenhouse gas behind climate change. They can provide relief from heat through shade and evapotranspiration.
• Solarize Philly, a rooftop solar program of the Philadelphia Energy Authority. Switching to renewable systems like solar power is a critical part of reducing greenhouse gas emissions and making energy sustainable.
• The Energy Poverty Alleviation Strategy addresses the disproportionately high energy costs that many overburdened residents face.

The Philadelphia Office of Sustainability (OOS) also leads programs and initiatives designed to prepare the city for extreme heat and build heat resilience.

• The Strawberry Mansion Cool Neighborhood Plan, in partnership with the Strawberry Mansion Community Development Corporation, is working to reduce the neighborhood’s heat risks.
• OOS is working with Climate Resilience Partners and residents to update the Climate Resilience Plan. The plan will address climate issues citywide.
• OOS is testing how different road and roof materials can help neighborhoods beat the heat.
• Cool Pavement Pilot in Hunting Park.
• Cool Roofs Pilot, in partnership with the Strawberry Mansion Community Development Corporation.
• The Community Resilience and Environmental Justice Fund provides grants to community-based organizations working on environmental justice projects, including projects on climate emergency preparedness, energy burden, and heat resilience.

The City also has many resources to help residents prepare for extreme heat and respond to heat emergencies. Check out those resources at How to Stay Safe.