Poland's climate is characterized by hot summers and dark, cold winters. Unless you're heading to the Tatras to ski, avoid travel from January to March. Many of the attractions are closed for the season, and the cold and snow make getting around difficult. Note that Kraków and Zakopane are both popular Christmas and New Year's destinations and hotel prices rise accordingly. Summer brings good weather, but more crowds as Poles take to the roads on their summer holidays. September and October are ideal, with fewer crowds and usually reliably good weather.
Holidays
Offices, banks, museums, and many stores are closed on the following holidays, though some stores and restaurants remain open: January 1 (New Year's Day), Easter Sunday and Monday, May 1 (State Holiday), May 3 (Constitution Day), Corpus Christi (falls on ninth Thurs following Easter Sunday), August 15 (Assumption), November 1 (All Saints' Day), November 11 (Independence Day), and December 25 and 26 (Christmas Day).
Major Festivals in Poland -- The calendar is filled with festivals of all kinds, with the most popular celebrations connected to religious dates or Poland's folk or cultural traditions. The annual Marian pilgrimages culminate in August at the Jasna Góra shrine in Czestochowa for the Feast of the Assumption on August 15. Warsaw, Kraków, Wroclaw, and Poznan all host jazz, contemporary, and classical music festivals throughout the year. The best idea is to check in with the local tourist information offices when you arrive to see what's going on during the time you're there. Kraków's Kazimierz district hosts the increasingly popular Jewish Cultural Festival every year in late June and July. Klezmer music concerts, films, and cultural discussions highlight the agenda. Zakopane and the surrounding area is the epicenter of the country's folk fests, with the biggest draw being Zakopane's Mountain Folklore Festival in August.