Bochum is a year-round destination — most of the main attractions are indoors, and the Mining Museum and Schauspielhaus operate regardless of season. That said, spring and early autumn are the most pleasant times to visit, with mild temperatures and the Stadtpark in good shape.
Summer brings the city to life outdoors. The Bochum Total festival, held each July in the city centre, is one of the largest free music festivals in Germany, filling the streets around Bermuda3Eck with stages over four days. It draws hundreds of thousands of visitors and books a mix of local and national acts across rock, pop, and electronic music.
Winter can be grey and damp, as is typical for the Ruhr. The Christmas market in the city centre runs through December and is a decent excuse to visit. Theatre season runs October to June, so winter is actually a good time to catch a production at the Schauspielhaus.