Vienna is warm and sunny in spring and autumn; July and August can be hot and stormy, with temperatures reaching well above 32ºC (90°F). From November through March, winter can get cold, with snow falling in January and February; lows of -12ºC (10°F) are frequent. Culturally, high season in Vienna is May, June, and September, when festivals, marathons, concerts, and operas are in full swing. In winter, the glittering Christmas markets attract international crowds and during the Ball Season, December through February, nearly 500 balls take place, hosted by nearly every profession or trade; the Coffee House Owners Ball is the biggest, the Opera Ball the most internationally famous. Many Viennese leave the city in July and August, so the city tones down some, though it fills with tourists.
Christkindlmarkt (Christmas Market). In Vienna the biggest Christmas market goes up in mid-November in the plaza in front of the city's Rathaus (town hall); there are more than 30 smaller ones dotted around town, including outside Schönbrunn and the Belvedere Palace, in the Spittelberg Quarter on the Freyung square, and in front of Karlkirche on Karlsplatz.
Donauinselfest (Danube Island Festival). Held in late June, this is Europe's largest open-air music fest, attracting 3 million visitors each year. Entrance is free. Donauinsel, Vienna. www.donauinselfest.at.
Fasching. In February, Fasching (or Fasnacht, as it's called in the western part of the country), the Carnival period before Lent, can get very wild, with huge processions of disguised figures and the occasional unwilling participation by spectators.
Hofburg New Year's Ball. Vienna's Ball Season, in January and February, kicks off on New Year's Eve with this glittering—and expensive—event (formerly known as Kaiserball), held in the elegant rooms of the Hofburg. 01/58736–66214. www.hofburg.com.
Wiener Festwochen. This festival of theater, music, film, and exhibitions takes over Vienna from mid-May to mid-June. 01/589–220. www.festwochen.at.
Wiener Opernball. One of the year's biggest society events is the Vienna Opera Ball, held the Thursday before Ash Wednesday at the magnificent Staatsoper. 01/5144–42250.the Staatsoper 01/514–44–2606. www.staatsoper.at.
Wiener Philharmoniker. The New Year in Vienna is greeted with a concert by the Vienna Philharmonic. Reserve a year, or even more, in advance. 01/505–6525. www.musikverein.at.
Volksoper. The opera season runs from September through June. If you can't get into the Philharmonic concert, try for one of the performances of the Franz Lehar operetta Die lustige Witwe, or another light delight. 01/5144–43670. www.volksoper.at.