Leicester has a temperate climate typical of the English Midlands: mild summers, cool winters, and rain year-round. There's no particular season to avoid for visiting the museums and historic sites, since most are indoors.
The unmissable time to visit is during Diwali (usually October–November), when Belgrave Road is illuminated and the city hosts one of the largest Diwali celebrations outside India, drawing tens of thousands of people. The street celebrations are free and genuinely spectacular.
Leicester Comedy Festival in February is one of the UK's longest-running comedy festivals and brings a good range of acts to venues across the city. The summer months (June–August) bring street markets and occasional outdoor events to the town centre.