September mornings in Tbilisi are generally mild with temperatures ranging from 15°C to 20°C (59°F to 68°F). It's best to wear light layers such as a long-sleeve shirt or blouse paired with a light jacket or cardigan to keep comfortable during early hours.
Afternoons tend to be warm, often reaching up to 25°C (77°F). You can opt for short-sleeve tops, lightweight trousers or skirts, and comfortable shoes suitable for walking around the city's Old Town and Rustaveli Avenue.
Evenings can be cooler, especially later in the month, so having a warmer layer like a sweater or a light coat is advisable. This will help you stay cozy while enjoying nightlife spots like Fabrika or dining along the Mtkvari River.
If you plan to stay longer in Tbilisi during September, consider packing additional versatile layers since the weather can fluctuate between warm days and cooler nights. For a shorter trip, focus on lightweight and breathable clothing with a single warmer jacket to cover all situations.