Lviv is pleasant from spring through autumn. May and September are excellent: mild temperatures, fewer crowds than July and August, and the city's many outdoor cafes operating at full stretch. Summer (June–August) is warm, sometimes hot, and busy — Rynok Square fills with tourists and prices rise slightly. Winter is cold and can be snowy, but Lviv looks romantic under snow, and the Christmas market on Rynok Square in December is one of the best in Ukraine.
The Lviv Jazz Festival in late October attracts good international performers. The International Book Forum in September draws publishers, writers, and readers from across the former Soviet space. Check the schedule before travelling if you have specific interests.