Pack or skip
Thermal underwear for Tbilisi in September
Verdict
Skip it
Lows near 59°F — you'll overheat.
Why
Tbilisi in September averages highs of 79°F, lows of 59°F, 8 rainy days.
That climate means thermal underwear isn't pulling its weight. Lows near 59°F — you'll overheat.