2026-05-07 · people

Cities can be ten degrees hotter

Concrete and exhaust amplify heat waves. Poor neighborhoods often lack shade and AC.

When heat waves hit, cities can be ten degrees hotter than surrounding countryside — concrete and exhaust trap the heat, and poorer neighborhoods often lack shade or air conditioning. More than half of humanity lives in that built-up risk zone: 57% of the world's 8.2 billion people are urban residents as of 2026.

1 cell = 8.2 million people (0.1% of world population) · 1,000 cells

Context

The grid divides the world's 8.2 billion people into urban residents (57%) and rural residents (43%), based on the United Nations' World Urbanization Prospects — the UN Population Division series covering every country from 1950 to 2050.

Urban heat islands form where buildings and pavement absorb heat and exhaust adds more, keeping cities hotter than surrounding areas — by as much as ten degrees during heat waves. Within cities, poorer neighborhoods often lack shade and air conditioning, so the same heat wave lands hardest there.

The 2025 Revision of World Urbanization Prospects is consistent with the 2024 Revision of World Population Prospects and is used widely across the UN system, by research centres, and in media coverage of urbanization.

UN WUP urban 57% — heat island risk concentrated in built-up areas.