It's really when you get into the thousands though that SI prefixes generally start to be used, you don't see deca or hecto used that often. It's mainly because we're usually happy keeping three digits of precision in general conversation (185 degrees C, 250 metres, etc). After that we get a bit sloppy and start rounding, and that's where kilo comes in and we start talking about "1.25 kilometres" and such.

Add in the fact that people rarely need to describe temperatures higher than 1000 degrees C with any precision, (they'll just round to hundreds/thousands/millions usually) and that's why SI units feel weird with temperature.