Hypothermia starts under 35 C Around 0 C it starts snowing instead of raining, and standing bodies of water freeze. If you have plants outside and it's not win

Hypothermia starts under 35 C Around 0 C it starts snowing instead of raining, and standing bodies of water freeze. If you have plants outside and it's not winter - they will die if it gets under 0 C. If you're driving - the road will freeze under 0 C and it's pretty dangerous to drive fast in such conditions. I'd argue there's no more important air temperature than 0 C on Earth-style planets. For cooking 100 C is a reference (water boils), but it's a bad starting temperature because you start lower than that. It's important to show room temperature (around 20 C), boiling temperature (around 100 C) and the maximum useful temperature (around 250 C). So starting at 0 C makes sense.