I wonder what you mean here. What code exactly would get auto-vectorized? Parsing the temperature surely not, since it's not in an array of fixed-size fields.

once you've done the work to implement parsing as branchless bitwise operations on integers I think that code can be extended automatically to operate on larger registers

I think it would work if that was the only code in the loop. But the loop spans several more nontrivial operations, including hashtable insertion.