system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What allows me to exhale at different temperatures? For example, I can warm up my hands by breathing on them. While on the contrary, I can cool them off too.
gpt
You can only breathe out a single temperature: warm.

However, fast-moving air has the ability to pull surrounding environmental air into its flow (a process called "entrainment").  So when you purse your lips and blow, the air you're breathing out is mixing more with the cooler air around it, making the end product feel cooler.

To test this, get something like an empty toilet-paper tube, cover one end with your hand (lightly, so air can still escape), and blow through the other end.  Without much surrounding air to pull in, you'll find that the air you blow is warm regardless of how quickly you blow.