Heat Safety
Urban Heat Island Explained: Why Cities Stay Hotter Than Nearby Rural Areas
Why cities can be hotter than surrounding areas, how pavement and buildings store heat, and why nighttime heat increases risk.
Quick answer: An urban heat island happens when buildings, pavement, traffic, and limited vegetation make a city warmer than nearby rural areas.
Heat storage
Concrete, asphalt, and buildings absorb heat during the day and release it slowly at night.
That keeps cities warmer after sunset.
Local differences
Tree cover, parks, water, building density, roof color, and traffic can create big temperature differences across one metro area.
Neighborhood-level heat risk can vary sharply.
Risk reduction
Shade, reflective surfaces, green space, cooling centers, and heat alerts can reduce impacts.
Nighttime heat is especially important for health.