Temperatures fall rapidly in autumn, and snow is common over much of the country in winter.
Many coastal resorts close down completely, but the ski resorts are in full swing between December and February.
Spring is a great time to visit Bulgaria. The weather is warm, though evenings may still be chilly.
All the sights and attractions are open again after winter, and there are fewer tourists around. September is also pleasant.
Expect high temperatures, bright sunny days and warm evenings throughout Bulgaria during high season.
The Black Sea coast, especially, is at its busiest and most expensive at this time.