system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are humans more susceptible to sunburn on a hot sunny day, rather than a cold sunny day?
gpt
In the seasons when days are hotter, the sun typically has a more direct angle relative to the Earth. In colder seasons, the angle is increased, leading to less direct exposure. 

However, you can get sunburn in sub-zero temps. It all depends on the angle of the Sun/intensity of the UV radiation.