Bayis Sheini (corresponding to the “Classical period” in European history), was a warm period. It was probably warmer than it is today.
One didn’t find large Jewish communities in cold areas until the late Middle Ages (which is when a major cold period, lasting in the 19th century) began. Houses were generally built with good insulation and people dressed warmly (wool was the main fabric). You normally didn’t find people wearing their “summer” clothes while indoors during the winter. Jews rarely lived on isolated homesteads, since that would mean not having a minyan or schools.