system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do heatwaves, like the one currently affecting the UK happen?

One week, we can have a cloudless sky and the temperature be no more than 20-25°C. This week we have a cloudless sky and the temperature has reached approaching 40°C. What factors cause the huge difference in temperature?
gpt
Air on Earth doesn't heat up evenly due to the angle of the sun, weather, and geography (eg. water and land heat up at different rates). Sometimes a heated air mass from a warm region goes places where they normally don't - like to the UK. It's usually hard to predict where air masses go, but they have patterns. These patterns are changing - that's in part what we mean by climate change. So at the moment basically a hot air mass - which is more likely to exist as a result of climate change - is going to a place where they historically rarely go - which is also more likely to happen as a result of climate change.