May to September is the best time to visit. Summer brings long evenings and warm weather ideal for exploring the fortress and the Latgale lake district — the lakes are swimmable from late June through August. The Mark Rothko Art Centre is open year-round, making Daugavpils a viable winter visit for those specifically coming for the art, but winters are harsh, grey, and very quiet, with little tourist infrastructure operating. Shoulder months (May, early June, September) offer good weather with fewer crowds than peak summer.
The city holds an annual City Festival in August, with outdoor concerts and events that give the centre an unusual buzz. Outside this, Daugavpils keeps its own quiet rhythm regardless of season.