Bulgaria's most comfortable temperatures are found mid May to mid September. The country's climate is influenced by the Mediterranean and Black Seas, making for generally mild conditions throughout the country. Summer days rarely get too hot. In the mountains and in the evenings, temperatures are about 10 degrees F/5 C cooler than in the rest of the country, on average. The winter can be bitterly cold, snowy and damp, but health spas are open, skiing is good, and the concert season is in full swing. Be sure to take a sweater, even in the summer, for cool evenings.