Vienna is warm and sunny in May and June, and in September and October; July and August can be hot and stormy, with temperatures reaching well above 90°F. From November through March winter can get cold, with snow falling in January and February; lows of 10°F are frequent.
Culturally, high season in Vienna is May, June, and September, when festivals, marathons, concerts, and operas are in full swing. The ball season December to February offers everyone a chance to brush up on his or her footwork and the many Christmas markets attract crowds from all over the world.
Many Viennese leave the city in July and August, so the city tones down some, though this is also when you might find discounted rates at hotels.
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.
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.
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.
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.
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.
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.
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.
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.