Spring (March–May) is the best time to visit Vicksburg. The battlefield is green, temperatures are mild, and the azaleas that were planted by veterans' groups across the park bloom in early April. Spring Pilgrimage in April opens antebellum homes to the public that are otherwise closed to visitors — the most reliable way to see interiors not normally on the tour circuit.
Summer is hot and humid — Mississippi summers are not for the faint-hearted. The battlefield is best walked in the early morning or evening. Autumn brings cooler temperatures and good light for photography on the battlefield.
The Vicksburg Civil War Siege Anniversary is commemorated over the 4th of July weekend with ranger talks, living history demonstrations, and events at the National Military Park. This is both the best and busiest time to visit if your primary interest is the battlefield.