During heatwaves the fan is no longer sufficient. It can improve ac cold air spreading though. A fan alone will not help you when your walls are warm and when even at night outside temp is above 20dg and humidity is high
No, it's about combination of humidity and temperature called wet bulb.
Highest wet bulb we can manage is 35 degrees. Below 35 wet bulb, a fan helps. And that's my point. For comparison the most extreme wet bulb temp that hit London in summer 2026 was 26 degrees according to met office. (I can't find other peak 2026 wet bulb temps in Europe)