I think March — May and September — October are the best times to visit. We went in June/July and let me tell you, it was hot. Like, we could barely stand to be outside from 10am to 5pm in Berat. The heat was heavy and it’s inland so has no beaches or ocean to cool off in.

The heat was still intense in the coastal town of Vlore, Sarande, and Ksamil, but it was way more enjoyable for boat trips and beach days. The summer (June—August) is also the busiest tourist season, so you’ll skip some of the crowds if you visit in the spring and fall. 

In my opinion, winter would be too warm for snow (except for north in the Albanian Alps) and too cold for beaches. So I wouldn’t do it.