Some quick math:
For -30 deg F to + 300 deg F and 0.1 deg F you're talking 12-bit ADC (either external for analog sensor or internal to digital sensor).

For -30 deg F to + 1800 deg F and 0.1 deg F you're talking 16-bit ADC.

I'm with Alain on this; really? I'm not saying this is not doable; just pointing out the obvious. Hopefully we are already stating the obvious. If that's the case, then for the -30 to +1800: yeah thermocouples, amplifiers, probably of windows/ranges to get better resolution. For the -30 to +300: something similar to LM135 (probably break it out in ranges as well).