Heatwaves can be harmful to people's health, especially in Spain where they are becoming more frequent. A study looked at 12 Spanish cities to see how different types of heatwaves affect mortality rates. They found that cities with fewer heatwaves had a higher risk of death during them. However, the impact of heatwaves on mortality varied greatly between cities, with no clear pattern. This shows that the relationship between heatwaves and deaths is complex and depends on the specific characteristics of each city. Understanding these local differences is important for creating effective prevention measures.