Kelvin?
Feel free to correct me but I don't think Kelvin has negatives, it starts at the coldest temperature, or something.
Kelvin has the same measure as celcius, but begins at absolute zero.I think if you add like, 265 or something to any celcius, you get kelvin, might be the wrong number though.
Absolute zero is roughly -273oC
At temperatures up to -30 degrees celcius.
Down to?
Mindforget.Temperatures up to 243 K.EDIT: forget that is still wrong.
"As low as" would be the best way to phrase it.