Austria is stunning at any time of year. December to March is best for snowsports; June to October is perfect for hiking and biking. July and August can get quite hot and bring the risk of thunderstorms.
There is an almost constant stream of festivals and events across the country, including:
January/February: Mozart Week, Salzburg
February: Masked Ball Season, Vienna
March/April: Easter Music Festival, Salzburg & Vienna
May-June: Vienna Festival (arts & music)
July-August: Salzburg Summer Festival
September: St. Rupert's Fair, Salzburg (procession, fireworks)
September/October: Vienna Wine Hiking Days
October: Almabtrieb (cow parades) across mountainous regions
November/December: Christmas markets
N.B. please do not rely solely on this information for your travel planning
AUSTRIA: BY AIR
From the UK: carriers include British Airways, Austrian, easyJet, Ryanair, Eurowings, TUI and Jet2 - the latter serving winter resorts such as Salzburg. The flight time is around 2 hours from London.
Within Europe: in addition to the above, try Niki and Norwegian Air Shuttle.
You can travel from London to Vienna, Salzburg or Innsbruck in a single day by high-speed train. Or take a lunchtime Eurostar to Brussels, a Thalys high-speed train to Cologne and the excellent Austrian Nightjet sleeper train to Innsbruck, Linz or Vienna, arriving at breakfast time. See Seat 61 for more.