Why Austria rewards careful timing.
Austria is central Europe's geographic and cultural pivot, bordered by 8 countries, with one foot in the Alps, one in the Danube basin, and one in the legacy of the Habsburg Empire. The country reaches from the Pannonian plain in the east (warm continental climate, paprika cuisine) to the Vorarlberg Alps in the west (alpine climate, ski-resort civilization), with three radically different climate zones and four cultural sub-regions.
Three climate zones operate in parallel. Vienna and the east run Pannonian-continental, hot summers (regularly 30°C+, occasional 35°C+ heatwaves), cold winters (-5 to 5°C), and one of central Europe's longest sunshine records. Salzburg, Salzkammergut, and central Austria run temperate-pre-alpine, cool wet summers, snowy winters, frequent Föhn winds bringing dramatic temperature swings. Tyrol, Vorarlberg, and the high Alps run alpine-continental, cold winters with deep snow, mild summers, and the country's most reliable ski conditions.
Austria's shoulder seasons are unusually long and pleasant. Spring runs early-April through late June; autumn from early September through late October. The country looks its best in May (apricot blossoms in the Wachau Valley peaked late March/early April but cherry blossoms peak in May, Heuriger wine taverns reopening, beer gardens in Vienna's Stadtpark) and October (vineyards copper-gold in the Wachau, foliage at peak in the Salzkammergut, wine harvest festivals).
Christmas market season is one of the country's biggest tourism reasons. Markets open mid-November (date varies by city: Vienna's Christkindlmarkt at Rathausplatz around November 14, Salzburg's at Dom and Residenzplatz around November 20, Hallstatt's running just one specific weekend) and run through December 23. The biggest atmosphere is at Vienna's Christkindlmarkt (Rathausplatz, the country's most famous, with skating rink and 150 stalls), Salzburg's Christkindlmarkt (since the 15th century, in front of the cathedral where Mozart was baptized), and Hallstatt's one-day market (typically the Monday of the second week of December, book accommodation 6+ months ahead).
Austria is mid-range Europe, comparable to Italy outside Venice, more expensive than Eastern Europe, less expensive than Switzerland or the Nordics. Mid-range hotels run €140–200/night in Vienna in shoulder season, climbing to €180–300 in summer and Christmas market weeks. Salzburg hits its highest hotel pricing during the Salzburg Festival (late July through August), book 4–6 months ahead.
Austria has some of Europe's best mountain railways. The Schafbergbahn (Salzkammergut), Achensee railway (Tyrol), and the Mariazellerbahn (the Vienna-area mountain narrow-gauge) all run summer schedules from late April through October. Cable cars in Tyrol's ski areas run year-round at most major destinations (Innsbruck's Nordkette, Hochzillertal, Sölden's glacier).