Austin's two biggest events should factor heavily into your timing. The Austin City Limits Music Festival takes over Zilker Park for three days each October, drawing massive crowds and headliners across every genre. Book accommodations well in advance. South by Southwest (SXSW) runs for two weeks in March, combining music, film, and tech conferences into the city's biggest annual event.
Spring and fall are the best seasons weather-wise. Summers are brutally hot, regularly exceeding 100 degrees Fahrenheit, and winters are mild with only rare freezes. The wildflower season in March and April, when bluebonnets carpet the Hill Country, is particularly beautiful.