Thats the whole point. It doesn't matter, as long as you use the same cup for all the measurements. Imperial recipes are ratios that can be scaled to any cup size.
Or do what most people do and use a measuring cup, standardized size, cheap and available at basically any store.
Large versions of these are often used in greenhouses for temperature control, so they do in fact work as advertised.
Water is very good at absorbing thermal energy, far better than air. The moist pads are drawing thermal energy out of the air and storing it in the water, reducing the air temperature.
Some water eventually evaporates, but in a gaseous state this water still retains the thermal energy it absorbed from the air, causing a noticeable decrease in air temperature, as well as a slight increase in humidity.
Put a very dry cloth in front of the cooler to trap water vapor, every now and again relocate the now damp cloth outside of the room being cooled, and replace it with a fresh dry cloth.
Fahrenheit is better for weather, and I'll fight anyone about it.
We use Celsius in the lab because it makes math easier, it's great.
But Fahrenheit is basically a 0-100 scale of how hot it is outside and that makes perfect sense for describing outside conditions relative to human sensory perception.
Thats the whole point. It doesn't matter, as long as you use the same cup for all the measurements. Imperial recipes are ratios that can be scaled to any cup size.
Or do what most people do and use a measuring cup, standardized size, cheap and available at basically any store.