What does "setius" mean?

Latin Learning Latin
1

In Virgil Georgics III is this text, in a description (which makes me think of Ice Road Truckers) of a winter in the steppes back of the Sea of Azov :-

Interea toto non setius aere ninguit:
intereunt pecudes, stant circumfusa pruinis
corpora magna boum, confertoque agmine cervi
torpent mole nova et summis vix cornibus extant.

What does “setius” mean exactly? I cannot find it in my good big voluminous Latin to English dictionary. Google Translate when given “setius” alone translates it as “nevertheless”. Loeb bilingual renders “non setius” as “none the less”.

2

It’s a comparative form of secus.

3

Thanks.