30°C is 303 Kelvin. Half of that is 151 Kelvin, which translates into a fairly mild -122°C!
Takes out hockey stick
New strategy to prevent global warming: just freeze all of the CO2 out of the air!
Dry snow doesn't sound like too bad of a proposition on its own.
Reminds me of a time one of my friends was happy that it was going to warm up and said something like "it's going to be twice as warm tomorrow". It was going from maybe 20F to 40F or something.
That led to an interesting discussion.
This knowledge comes in handy with marketing BS around CPU coolers. If an aftermarket cooler gets a CPU to 35C when the stock cooler is at 70C, marketing will sometimes claim it cut temperatures in half.
Usually that should mean it cuts the difference ambiant and CPU in half. Anything else would just be stupid or a lie.
Let's say the summer average is 30⁰C or 303.15 Kelvin
The absolute coldest possible temperature is -273.15⁰C, or 0K.
Halfway between absolute zero and 30⁰C/303.15K is somewhere around -121⁰C/152K
So if it were half as hot in the summer, it would be colder than ever recorded on earth.
In short, you don't want to use a temperature scale with an arbitrary starting point for doing calculations like this. The freezing point of water is no more or less arbitrary than the freezing point of oxygen or sodium or anything else. It's just one that's somewhat useful for everyday use. When handling calculations for multiplying temperature, you want an absolute scale like Kelvin.
Or Rankine if you're that kind of pervert.
Probably want it between the winter temperature and the current summer temperature, but genies are traditionally fickle and pounce on any ambiguity