Approximately eight billion people are living on Earth today with more than half (55%, similar to 4.2 billion) living in cities-a proportion predicted to increase to 70% (similar to 6.6. billion) by 2050. As the human population grows, urban residents will face increasingly extreme temperatures under future climate change, which will affect human well-being, health, and mortality. However, nature-based solutions offer promising strategies to mitigate these impacts. Here, we analyst future projections of the maximum temperature of the warmest month, as a proxy for extreme heat exposure across 5646 cities in 218 countries. We show that by mid-century, this climate metric is projected to increase by an average of +1.7 degrees C (+/- 0.5 degrees C), with the largest increases (similar to 4 degrees C) projected to occur in mid-to-high latitude cities of Europe, North America, and Australia. We highlight the urgent need to adopt nature-based solutions to mitigate projected increases in urban heat and contribute to net-zero CO2 emissions goals.